They are so different from each other...Personally Far Cry 3 was a good game but it's not as fun as a Saints game.
If I were you, assuming you had 60 bucks to blow, I'd get Saints Row 4 and a copy of Far Cry 3 Blood Dragon. It's not as deep as Far Cry 3 but in my opinion it IS funner since you get to do a lot of crazy stuff since your character is a cyborg. In Far Cry 3 you just can't get away with half the stuff you can do in Blood Dragon.