Both are great cars and both work on asphalt.
The T-Fource is easier to setup and maintain. CRC's top guys run T-Fources (Rheinart, Groskamp, McMahon). They dont use the side springs though...just use the tweak screws in the t-bar.
The Carpet knife is cool if you want a change of pace from the T-bar cars. Despite the name it does work on asphalt it just needs a little more work to get dialed in.