I think that bass is best, when you use no effects - in master of puppets Newsted (or Burton) didn't used any! I don't know much about Fear Factory, but I can assure you that 85% of whole metal bass is just a pure bass sound - are you playing in some band ? Or you want to play at home for yourself ?
Ps. If you use distortion or overdrive box your bass will sound not like instrument but farting
and that's not good !