Pathfinder intentionally made races a tiny bit more significant by increasing their net ability score bonus to +2 from +0. Humans, in particular, went from having only the slight drawback of being unable to get 20 in their highest ability score to none at all, making them very-nearly-always the best choice for almost anything you’d want to do.
But really, aside from the ability score bonus, the differences are negligible compared to the imbalances already present among the races within in a single system. In both systems, the humans’ bonus feat makes them usually the best choice, and when not the best choice, always in the top five or so. In both systems, half-elves and half-orcs are pretty mediocre, though Pathfinder did a lot to improve them, particularly with the alternate options available to them.
So by “upgrading” all 3.5 races by giving them +2 to another ability score (or downgrading all Pathfinder races by removing a +2), you’ll achieve balance at least as good as found in 3.5 alone or in Pathfinder alone. Which will still mean humans are dominant, but oh well. That was always true.
Classes in Pathfinder, like classes in 3.5, are very wildly imbalanced. As in 3.5, magical classes are dominating, and mundane classes struggle. This is true both of the core classes that both systems share, and the new classes that Paizo has added.
Core Classes – What’s Changed?
For the most part, classes saw small, almost-inconsequential boosts in power. There are some notable exceptions, though seeing as most of those were kind of significant boosts to already-extremely-powerful classes (cleric, druid, sorcerer, and wizard), in practice that may not matter that much. Only the paladin was weak and saw large improvements, and even there it didn’t turn the class into any kind of powerhouse.
However, notably, quite a few classes that received apparent boosts were actually nerfed in Pathfinder by changes outside the actual class description. Changes to feats, and various options that 3.5 had in supplements that are not replicated or replaced in Pathfinder, constitute a pretty consistent stealth nerf, typically aimed at mundane classes.
For example, a Pathfinder fighter who can take 3.5 feats is a bit – not a lot, but a bit – better than a 3.5 fighter. On the other hand, a Pathfinder fighter who is restricted to Pathfinder feats is quite a lot weaker than a 3.5 fighter who is restricted to 3.5 feats – and that’s even if we give the Pathfinder fighter the feat-every-odd-level and not the 3.5 one.
As another example, later 3.5 supplements made a consistent effort to give mundane and martial characters relatively easy access to the ability to move and attack effectively. Complete Champion offered Pounce from a single level of Barbarian, or Swift-action movement for a minute per day (or more) as a feat. Tome of Battle gave martial characters useful standard actions. Paizo has consistently avoided giving its mundane classes similar options for mobility. The Barbarian still can get Pounce, but only at level 10, only while Raging. While both the druid and summoner can get Pounce in the first few levels.
So while the changes have been very small, I will say that I find some of Paizo’s decisions about magic vs. mundane troubling: 3.5 had a long history of making magic highly dominant, forcing mundanes to pay a “realism tax” that the magic-users ignored entirely. Paizo continued and in some cases reinforced this trend.
It’s almost like – and this was true in 3.5, but Paizo has done nothing to fix it – magicals and mundanes are literally playing different games. Stuff that mundanes cannot do, magicals can do easily because “magic” – but the reverse is not really true.
Paizo’s new classes followed most of the trends set by 3.5: the new magical classes are quite powerful, the new mundane classes are decidedly not powerful, and the gap remains. I don’t think any of the new classes is more powerful than the most powerful classes in 3.5, and I don’t think any of the new classes is weaker than the weakest classes in 3.5, so ultimately adding Pathfinder’s new classes doesn’t do much about the total power variance in the system.
I’d probably allow the changed Pathfinder classes, as well as the new classes. I might ban the bonuses to the highest-powered classes, but most of those are small and with or without them, those classes will still be dominant. I tend to rely on gentlemen’s agreements and trust in my players to deal with them.
I’d also probably be willing to allow new feats. In most cases, I would prefer the 3.5 version of shared feats, and I’d certainly want to keep the 3.5 feat library open.
Combat maneuvers, I’d probably keep the 3.5 version. They were stupid and overly-complicated, but I don’t like the math of Paizo’s fix, and I wouldn’t be overly interested in fixing it.
Skill consolidation is a good idea and I’d get behind that. Actually, I already had my own set of consolidated skills before Pathfinder was ever a thing, so whatever. I don’t think Paizo went far enough.
Spells are a mess in both systems. It almost doesn’t matter what you do, unless you rewrite all of them (not just some like Paizo did). The polymorph changes are probably worthwhile; I tend to soft-ban them in my 3.5 games, and if a player was really interested in a shapeshifting character I would consider the Pathfinder versions. Paizo’s completely new spells are fine; some of them are very powerful, but then so were the ones that were already in 3.5.
Races, I’d want to handle the extra +2 that Pathfinder gave somehow, but that would be my only concern.
Overall, the thing to remember is that Pathfinder is really nothing more than a series of houserules on 3.5. It doesn’t change anything fundamental about the system, and certainly doesn’t fix any of those fundamental problems – but it doesn’t really create any new fundamental problems, so that’s a wash. A number of the changes are good, a number of the changes are bad, but ultimately all of the changes are small.