I should also add that I much prefer Sprints/Classics for general jogging/walking/exercise and Trek Sports for anything on rougher terrain (e.g. hiking in rocky areas, trail running in muddy areas).
The Trek Sport sole is stiffer and thicker than the Sprints/Classics -- pretty much all of the VFF line is thicker than the Sprints/Classics -- and I really like the groundfeel I get from the simpler soles. Much closer to true barefoot. That said, the Trek Sports are borderline as to whether they really offer enough extra protection for hiking on rocks for too long -- eventually, your feet will be really sore.
For me, the biggest plus to Trek Sports is the additional traction if you're doing a lot of distance on loose/muddy/slippery surfaces. The traction of the Trek Sports over the Sprints/Classics is significant on poor surfaces. On concrete, dry grass, etc, the Sprints/Classics are at least as grippy, if not moreso, than the Trek Sports.
If you've got the money, I really like having both sole options in the closet, each for different conditions.