I've finally understood why I like Fallout more than Arcanum. Not really difficult if I analyze various aspects of Fallout-like games that make them good. They are: non-linearity, character variety and quests variety. To put it simple: when Fallout-like RPG is linear, you can only create one kind of character and all quests look similar, this is no longer Fallout-like RPG.
As for character variety, Arcanum actually beats Fallout. You can always try melee/HtH combat in Fallout or throwing grenades at your enemies or even avoid fighting altogether, but that's simply no fun. There are not many HtH and melee weapons in Fallout, and even less good ones. Oh, and when I'm talking about Fallout, I'm talking mostly about Fallout 2. Grenades are not fun either. There are maybe two kinds of them. So, if you want to progress with your weaponry and actually have a choice what to use, go with small guns. You may wish to opt for big or energy guns as well, but you have not many choices of them either. Laser weapons suck, pulse ones are good, but can be troublesome when fighting floaters and picking up loot from disintegrated bodies. So plasma weapons are probably the best choice from energy. As for big guns, the Bozar is arguably the best. You may wish to go with Vindicator if you manage to find enough ammo (which is unlikely) or maybe even Avenger, but the Bozar is better and can be obtained pretty early. And besides, you need ST 6 to use either, which is kind of a waste until you find the power armor and when you do, you might as well stick to the Gauss rifle from that point on. As for non-combat skills, things are pretty simple in Fallout: if you have high IN (which you should), even with the gifted trait you have more than enough points to boost all the necessary skills: speech, lockpick, science, doctor, repair, steal and sneak. Can't think of much else. Well, you can't boost all of them to very high level, but you don't need that either. Great speech, good science and lockpick and decent other skills pretty much do the job.
So, what do we have in Fallout? All-skilled generalist with small guns with some not-so-fun options like big guns, energy weapons, proficient thief, stupid character etc. Let's see what Arcanum has to offer.
First off, you can't simply max out everything you'll ever need, and that's good. Partly this is because of the level cap, which is bad. Fortunately, I've written the nearly universal level cap remover, but even with it in place, you simply won't have enough exp to advance beyond, say, level 70. Unless you employ some boring level-up technique, which is silly. So, you have to choose what your character is, and choose wisely. You should go with persuasion, but you may want to stop advancing it beyond the expert level. You can choose magic, technology or neither. I personally have never been able to beat the game without magic or with technology, but I know many people have, and they had fun too. You can go with thieving skills which is fun, but you can also drop them completely and the game will still be fun. You can use melee weapons, throwing weapons or the guns. All three are fun, though I have never used guns myself. Also, you have many races to choose, of which at least humans, halflings and half-ogres present very nice and very different choices. And even if you choose the magic path, you still have 16 colleges of magic to choose from, and a lot of them are very good, such as conveyance, white necromancy, force and temporal. As for weapon choices, throwing weapons offer you less, but they are very good, fast and nearly unbreakable. Don't know much about guns, but melee weapons present very many good choices.
But that's about all that is good about Arcanum. Let's talk about non-linearity instead. Basically, you have two main quests in Fallout - find the drat GECK and kill the bad guys, that's it. Now, when you leave Arroyo, after you've done with Klamath and the Den, you have a lot of choices where to go, which can't be bad. Let's see - you have Redding/New Reno/Vault City choice after the Den, you can stumble into Modoc on your way to the Vault City and soon after that, you also have NCR and Broken Hills - say, you can go to Redding and take the caravan to NCR which pays $2000 and a lot of exp and loot. Thus the mid-part of Fallout is mostly non-linear. When I was playing it the first time, I actually end up in the Vault City at the very end of the game, just before going to Vault 13, Military Base and San Francisco. And I even managed to miss Modoc completely.
Thus we the following sequence in Fallout 2: Arroyo -> Klamath -> the Den -> everything else -> San Francisco. Not very linear, is it? Good. Now let's talk about Arcanum.
The beginning of the game looks promising. I must say that it also goes for the most of the modern games, some of them tend to get rather crappy towards the end. Fortunately, Arcanum isn't that bad, but still suffers this symptom. When you're done with Broken Hills, which is rather good, you have the choice of Tarant and Dernholm. Good choice. Then you can go to Ashbury and Blackroot. Good choice again, but guess what? This is the last one you ever get. Let's see. When you're done with the Black Mountain mines, you are going to the Isle of Despair. This is the only time you can get there, but that's explainable. You can even get back if you manage to find the secret "free teleport" location, but that's pointless. After that, and no earlier than that, you must go to the Wheel Clan. After that, Stillwater. After that, Quintarra. Then Caladon. Then Roseborough. Then T'Sen-Ang. Then Thanatos. Then Tulla. Then Vendigroth. Then the Void. What the gently caress? Why on Earth can't I go back to Caladon where I have come from? Why every magic shop sells Stillwater blades but nobody knows how to get there? I must confess, the storyline itself is good, but there is not much to do in between unless you left incomplete quests in some cities, which is kind of silly. Like, do one thieves' guild quest, then go to P. Schuyler and sons, then do another quest, then go to
Okay, what about quests? Quests should be different and fun. Boring and repetitive quests are bad. At first sight, it seems that both Arcanum and Fallout are good. But let's not get ahead of ourselves. Let's see about Fallout. Arroyo has a few quests, but that's only the beginning. Klamath is good. The Den is great. Modoc is good (blowing up the outhouse is fun). The Vault City is very good. Broken Hills are very good too. The New Reno is excellent. The Raiders quest has a boring fight in it, but much else as well. NCR is great except for the boring fight in the Vault 15. Redding is nice except for the boring fight with Wanamingos. Vault 13 is boring, Military Base is nothing more than a fight. San Francisco is good enough, and Navarro and the Enclave are so-so. And while I keep talking about those boring fights, please not that only two of them are similar: raiders and bandits in the Vault 15. Wanamingos are different for obvious reason as well as rats in Klamath and ants in Broken Hills. Fighting criminals in New Reno can be tedious, but you can complete most of the quests without doing that. Basically, you have different type of enemy each time you must fight a lot of enemies for a quest, excluding Vault 15 and raiders. As for not-fighting types of quests, they are generally OK.
Let's see about Arcanum now. Not counting wolves/pigs/rats in the beginning as I didn't count the temple of trials in Fallout. Rats in the Bessy Toon mine. Undead in P. Schuyler and sons. Rats in the Tarant sewer. Undead and Shamblers in the old Tarant sewer. Undead and Shamblers in the Ancient Maze. Undead in the necromancer castle in Ashbury. Undead in the Ancient Temple. Golems and bandits in the Black Mountain Clan mines. Spiders in the Wheel Clan. Animals and golems in the Wheel Clan. Animals in the Hardin Pass. Animals and golems in the Gorgoth Pass. Undead in the Caladon sewer. Fire elementals in the Pits of Fire. Animals on Thanatos. Finally some different monsters in Vendigroth and the Void. By the end of the game you usually get sick of fighting animals, undead and golems. The fact that golems damage melee weapons doesn't make it any better. Now, of course you don't have to fight in all that side areas that even have nothing to do with any of the quests, but let's see what we end up with doing the main quest only (which is kind of silly): undead in P. Schuyler and Sons, golems and bandits in the Black Mountain Clan, animals on Thanatos, spiders in Vendigroth. That is, if you have enough diplomacy to avoid fighting undead in Caladon and golems with animals in the Wheel Clan. Now if we talk about non-fighting quests, let's see what we can come up with. Shrouded Hills is excellent, and so is Tarant. Dernholm is somewhat boring but good nevertheless. Blackroot and Ashbury are good. Oh, I have forgotten to mention yet another undead fight: I mean the quest for Geoffrey, of course. Isle of Despair is so-so, as well as Stillwater and Quintarra. In the Wheel Clan most quests are boring fights. Caladon is nice, but that's all we get before the end of the game. Since in Roseborough we have a huge inn in the middle of nowhere and not much else.
So, what do we have? An excellent, non-linear game with a lot of different quests and some fights albeit with small guns only on the one hand, and long, mostly linear game with a lot of boring repetitive fights but with some character creation freedom on the other hand. Hmm... let me see... well, both games are very good and fun to play, but I think the winner is obvious.