Honestly, there weren't many game-breaking bugs in Ultima 4. The few bugs that exist (https://ultima.fandom.com/wiki/Bugs#Ultima_IV) don't exist in xu4.

Mainly, the Ultima Patcher (the 1.0 and 2.0 versions) have QoL improvements, most of which are in xu4 as "C"onfigurable options that you can add/remove in the title screen. The one configurable option that I really enjoy in 2.0 (that does not exist as a "C"onfigurable option in xu4) is the ability to attack diagonally, since I always found that it was silly that Enemies can attack you diagonally, but you can't attack THEM diagonally. But for the most part, almost every QoL feature exists in xu4 as a configurable option.

The "VGA Upgrade" is a mod that you can turn on/off in xu4 in a non-intuitive way. Instead of accessing that via the "C"onfigure menu, you hit Esc, and then select it manually. That's true also for the music mods in xu4.

For the most part, the difference between using DOSBox and patching using Pix's Patcher or playing using xu4 is in the UI and music options. The music options are different using Pix's Ultima Patcher vs. the mods available for xu4. Also, the QoL features are automatically installed for you with Pix, whereas with xu4 you have the ability to configure and turn on/off each and every QoL feature you can think of. Which may either be a positive or a negative for you.

Many thanks for your reply.
Thats exactly what I wanted to hear.
I use XU4 with the VGA pack and I also used the Hythloth fix an addition.
I use the basic music that comes with XU4, but I think it sounded better with Pix Patcher.
Is there a music update for XU4 available or just different music sets?

I only know of the 3 music modules on the xu4 download page (https://xu4.sourceforge.net/download.php)

Aradindae Dragon
Voyager Dragon 1.1
Voyager Dragon 1.2

They are also activated by hitting "Esc" and then selecting one of the modules.

There may be other music modules that exist for xu4, but I don't know where they might be.

They are pretty good, but, IMO, the music options are better for the normal version of Ultima IV that can be played via DOSBox than for the xu4 engine. There is a fairly large subset of Ultima fans who don't use engines like xu4, Nuvie, Exult, simply b/c they prefer the music when playing the game using a DOS emulator.

I have a different reason for preferring to not use these engines; I find that they're not mechanically faithful to the original version.

In xu4, for example, it seems that the enemies do very little damage to the player, at least when I tried it. There's a difficulty selection, but all it seems to do is affect the accuracy of your attacks, which feels like the worst way to adjust the difficulty, as it is not fun when you keep missing over and over.

Exult, as of when I last checked, has HP and MP regen wrong. In the DOS game, you recover 1 HP and half your spent MP each hour. (I find the "recover half spent MP each hour" mechanic rather interesting; it's too bad magic had to also be saddled with the requirement for reagents, but that's for another topic.) In Exult, however, you recover a random amount up to 1/3 of your maximum HP and MP each hour, which feels less interesting to me, and also involves a bit too much randomness.

Edit: My favorite way to play Ultima 4, when I want to play a version that's reasonably faithful to the original (that is, not the NES version), is actually the Sega Master System version.

Hmm, maybe that has been fixed? I just ran a test using the latest snapshot of xu4 and the GOG version of Ultima IV. For xu4 I created a bard with STR 16, DEX 24, INT 22, and Cloth armor and a Sling. With the GOG version of Ultima IV, I created a bard with the same dex, specifically STR 19, DEX 24, INT 16, with Cloth Armor and a Sling.

Then I went to a bridge with a single bridge troll, walked up to it, and let it melee me a bunch.

With xu4, the damage went as follows:
300
281
276
268
263
258
252
251
247
243
238
233
220
204
202
197

With the GOG version of Ultima IV, the damage went as follows:
300
295
282
279
269
260
257
253
241
238
234
232
229
224
220
217
215
211
204
185

Then, I modified xu4 to Expert mode (the mode I prefer to play with) and did the same thing. My damage in Expert mode went as follows:
300
256
220
198

That being said, I still prefer playing the GOG version of Ultima IV b/c I like the ability to attack Foes diagonally the same way the Foes can attack me diagonally, AND the music is better. =P~~~

So i tried a bit around in both versions.
At first I really liked the look of XU4 better.
I like that characters don't have the black block around them. I liked the option to color the game text.
And the smooth filter looks nice too.

But after I while I came back to DOS version with full Pix Patcher.
I want to play U5 afterwards and I decided that XU4 differs to much from the original look.
But the quality of the music is great with the sound modules although I like the original themes a bit more.

The Sega Master System also allows attacking diagonally, or in any direction as long as the enemy is within range (and slings don't go all the way across the screen in the SMS version). With that said, attacking diagonally, I believe, can trivialize certain rooms.

I also note that the damage you take is higher in the SMS version than what you reported for the GOG version, or xu4 on normal.

The SMS version is actually my preferred version if I'm looking for a non-NES version of the game.

(By the way, the NES version does allow attacking diagonally with ranged weapons; in fact, you can attack an enemy anywhere on the battlefield with one, even if it's behind a wall, though trying to attack an adjacent enemy with a bow will result in you using what you have equipped in the "sword" slot instead (or unarmed if the bow is your only weapon). On the other hand, I think I prefer the original music to the NES music, even though the NES version has more tracks, like one specifically for room battles, and one specifically for abyss hallways.)

It can, but for me I mainly care about fairness. If Foes can attack me diagonally, I want to be able to attack them diagonally. If they can't attack me diagonally, I'm totally fine not being able to attack them diagonally. I just want the attacks to be flowing both ways along the same paths.

I didn't know that about the Sega and NES versions. Good to know. I think my next playthrough will be the C64 "Ultima IV Remastered v 2.2.1" version. It looks well-done and highly rated, and I've never played any C64 version before.

Worth noting that these versions do give enemies the same ability to attack you from arbitrary directions. The way walls interact with weapons is the same for enemies as it is for you; they go through walls on NES, but not SMS.

By the way, the NES version is very different from the others. There's a lot I like about the NES version, particularly the combat mechanics (you can't miss with melee, your ranged attacks aren't going to repeatedly miss the same enemy, damage is less random, you can equip a melee weapon and a bow (or sling, but not magic axe or wand) at the same times), but there's also things that aren't so good, like the simplification of dialog and dungeons. It's definitely worth playing simply because it's such a different experience, yet it's still good.

Worth noting, however, that the NES version of Ultima *5* should be avoided; it's bad enough to be considered kusoge, getting even basic things wrong (game eats inputs, can't regain MP unless you die, having only one annoying music track for the entire game (and no sound effects IIRC), and the like).

What are your thoughts on the SNES version of Ultima 7? The few videos I've seen of it are a bit cringey...

It's definitely not the same game as the PC game with that name, and should not be treated as the same game, even if the plot line is similar.

I have mentioned, many times, the issues I have with Ultlma 7. It turns out that the SNES version is different enough that, surprisingly, none of those issues apply to the SNES version.

Note that I have not played it, but I have seen videos of someone speedrunning it.

So, don't expect the same Ultima 7 you're used to. If you go in without that expectation, it might actually be a decent game.

By the way, SNES Ultima 6 is basically a simplification of the PC version. You can't manually start combat (and you can't attack non-hostile NPCs), and some spells are missing (Enchant most notably; the others tended to either be useless or be only good for exploits, though I note that I believe Armageddon is also missing), but the game is otherwise mostly intact, and even the graphics and sound are similar. (The Ultima 6 OST sounds quite nice on the SNES sound chip.)