I've found that I prefer the PC version for Ultima 3, even though it does have the issue that enemies are too rare on the main world map. Specifically:
* Enemies don't scale with your level, so you can level up without worrying about powerful enemies appearing.
* Druids with high scores in both mental stats recover MP faster, a mechanic not present in the NES version.
* Getting a ship the intended way may require a lot of luck, but fortunately there's an exploit that allows you to get a ship without having to rely on RNG.
* The game plays much faster.

I've also tried the Commodore 64 and Amiga versions, and I still prefer the DOS version:
* C64 version is annoyingly slow.
* Amiga version has a busted RNG (it is very streaky), and certain things (like poison) are slow; also, you can't actually turn off the sound to speed things up. (Also, note that Rangers get as much MP and MP regen as Druids (except that INT and WIS are checked in reverse order), making Druids, Alchemists, and Illusionists pointless in this version.)

By the way, I forgot about one area effect spell in Ultima 4 NES: The Energy spell, in addition to doing damage to its target (similar to Missile, Fire, or Ice), will create a 3x3 lava field centered on the target. (Note that this is not how the spell works in the PC version.)

See?!? I didn't know even that. Only you know it that well.

The only time I recall playing Ultima IV was trying it out on Amiga, but I didn't start to play it properly. Too many other interesting, and visually more appealing, games on Amiga...