Op, I guess it boils down to what you want. AFM is deeper, and the rules have more substance to them, but the playfield is simple and somewhat uninspired. That isn't a bad thing, however, since sometimes simplicity is the ultimate sophistication.
Creature is a little cluttered, but it's complexity is what makes it really fun to shoot at. I think the art package on creature is among the best of any pin as well. Absolutely gorgeous.
If it were me deciding between the two, I think my decision would come down to how large or diverse my collection is. In larger collections, I might have to go with creature, but in smaller collections, I'd rather have AFM.