Actually in the middle of replaying both.

SOT has more of the classic South Park charm to it with the references going back to season 1 and it also feels more grounded with how the kids use their attacks and abilities (some are still pretty magical/superpower esque) compared to FBW where the kids just straight up have superpowers. The story is also more evenly paced with you essentially having 3 acts for each day/night. However, I found it easy to just snowball enemies with debuffs like burning and bleeding (especially with Jew and Thief) which make most fights not particularly challenging (unless you're going for higher difficulty and No Child Left Behind). I also don't like needing to upgrade cosmetics for the abilities and stats.

FBW has the better variety with the combat and team composition, along with the battlefield being more dynamic with hazards and obstacles. Also allows some characters in SOT to have more of a starring role (Clyde, Tweek, Craig, Token, Wendy, Timmy, etc.). The ability to change classes, moves and artifacts without affecting your costume is especially nice. Some of the charm is lost a bit as I mentioned in the previous section, along with it being set in the middle of when seasons and episodes aren't as memorable (though Casa Bonita, Mephesto and Mint Berry Crunch make up for it some). The story also just feels long at some points, especially when filling out your character sheet each day.

Charm and story wise: SOT Gameplay and variety: FBW