tux_ Isn't the one Android ships with good enough?
Tolerance to inaccurate typing (because of protective glass/film, etc - Gboard is almost perfect in it, FUTO is not there yet either, unfortunately), lack of voice input, lack of alternative symbols, lack of floating mode, weaker dictionary/prediction (at least it looks so to me).
I use FUTO atm as I try to avoid google services as much as possible, and it's okeish, though when I use gboard on other devices, I immediately notice the difference.