We currently in the process of preparing to frame our 2-story, 3,000 sq. ft. home (crawlspace) and are being told two very different things by 2 different contractors regarding the type of floor joist which we should use. One framer is telling us that, assuming he culls properly, using 2x10's are just as good as engineered floor joist for half the cost. The other swears by the I-beams. Pier spacing will be 8 ft.(per prepared plans). Any thoughts out there?

Unless there are very long spans, or some other reasons to choose composite joists, dimension lumber is perfectly acceptable. Your framer said the key words..."properly culled". The better the grade of lumber you use, the less culling will be necessary also. Be certain that the subfloor is glue-nailed to the joists, it enhances performance and reduces squeaks.