LogFAQs > #966044700

Switching to Assassin will increase your strength (damage) growth while sacrificing a bit of health and defense for some Stamina (which is needed to spam your special attacks). You do get to keep access to your shield as the assassin. You don't need to equip a bow, which is nice. The basic fighter class really is actually a very solid defensive choice you can stick with for the entire game, while the assassin lets you kill stuff faster at the expense of losing some of your defensive safety net.

The 2-handed warrior.... just kinda sucks. Stat gains aren't anything more useful than just specializing as a sword/shield fighter or DPS assassin. All of its skills are locked into its own 2-handed weapons which don't carry over to any other class. It does has some useful augments but you have to grind a bit to unlock those so it's hard to say if it's worth it. The one thing the Warrior does well is knocking enemies, even large enemies, onto the ground quickly. Which will let your pawns take advantage of the 2x damage bonus and just the general safety of large enemies not trampling over them.

I will say that the Fighter has good augments as well, and the assassin augments are kinda boring, and they also got nerfed in Dark Arisen. Might be worth it to stick with Fighter until you can purchase the good Augments. Then later on decide if switching to Assassin for better damage and stamina gains or sticking with fighter is more appealing. Alternately you can switch to assassin and gain a lot of strength early on, and then switch back to your fighter later on.

Bow access is kind of a wash. Personally I don't find the bow very useful but this is because I suck at aiming. I prefer to just recruit a pawn archer and let the AI do the aiming and shooting. As bad as the pawns can be at aiming and attacking enemies, it's usually fine as long as you're playing the melee focused character and keeping enemies locked down.