It's interesting that the Sport has longer chainstays of the Comp. Something different for '07 because of the different frames? I would try to ride both to see what the difference is for you in terms of ride. The '07 Sport has the same frame and Speedzertz fork as the '06 Comp. The A1 aluminum frame is nice, and light for a 'cross design. You don't get the Zertz seat post or handlebars, but you probably won't miss it. The component spec is fine also. The Sport is heavier than the Comp overall, but hey, you're riding to lose weight, so it's a wash.

The max tire size for the Tricross would be 38c. The Sequoia will not fit anything above 25-28c. That has to do with the brakes. Tricrosses have cantis (greater clearance), the Sequoia has dual pivot sidepulls.

The money you save getting the Sport you can use buying some good lights, rack, and bags. And oh yeah, there's no bell included, so you have to buy one!