In my 1st year of tris, I've done several sprints and plan to move up to olympic distance next season. I'm going to upgrade to a much better-quality bike and I'm about 90% sure it will be a tri bike from everything I've researched. I've narrowed it down to the 2011 Felt B16 or the Trek Speed Concept 7.0. A salesperson told me the Trek is worth a little extra $$ because it is more adjustable for a comfortable fit. If anyone could confirm or contradict this, I would appreciate any info!
First, those are two really nice bikes. Second, was he a Trek salesman? ;-) You'd probably be very happy with both/either. As for adjustability - I'm pretty sure the B16 will be as adjustable as any other tri bike out there, so I'm not sure where the salesman is coming from. Check slowtwitch.com, that guy does some pretty serious reviews of the + and - of both bikes.
http://www.slowtwitch.com/Products/Tri_Bike_by_brand/Felt/Felt_B16_for_2010_1145.html (sorry, this is the 2010 model, but I think it's the same mold)
But if those bikes fit your geometry well, then theoretically you should be very comfortable on either. Have fun shopping!
The B16 and SC7 both have a regular steerer setup (vs. the setups on the top-end Felts and Treks), so you can adjust either one equally via changing the stem and aerobars. If you put identical stems and aerobars on both bikes, the Trek arm position will be lower and further away from the saddle than the Felt. Depending on your current body position and thoughts on whether you'll get more flexible/comfortable getting a lower position, one will be better for you than the other.
The rep was rehashing the promo material on the SC9, which is touted as being more adjustable than competitors, but that's SC9 vs. Felt DA, Cervelo P4, and other "superbikes". At the SC7/B16 level, adjustability isn't an issue.
Personally, I'd be happy with either of those bikes. As long as the specific bike fits you and is adjusted properly, you'll be fine with either of those bikes.