I own both cars and run both cars all the time. The thing that is nice about the T-Fource is you can use the side springs instead of the setscrews in the T-bar. I find the car is much better and more consistant in this configuration.
In stock I find the T-Fource about .10 sec faster than the Knife. The T-Fource seems to hold it's speed in the turns better as compared to the Knife.