I've got a 5900 as my race bike and it is truly awesome! the road surfaces here in the UK are absolutely awful, but it gives a really smooth ride.
It's incredibly stiff and fast, particularly when climbing. A lot of people do question the durability of the carbon frames, but the bike this replaced was a 1994 OCLV 5500, still going strong! I shattered a pair of forks by colliding with a car which turned across me at 35mph, but the frame is absolutely fine, which seems quite impressive! If you prefer the more 'sprung' feeling of the ti frame then the Litespeed may be better, not quite as stiff as the Trek though.
Try em all and pick your favourite!