Whichever floats your boat. The TT, TT Pro, and Stripper are all the same frame with different finishes. The Pro, as the name and price suggest, has nicer components. The TT and Stripper are essentially the exact same bike, with different paint jobs. The WT has different geometry (I believe?) and fits huge tires (just ask gysewho). The S3X (if they still sell it) has an internally geared fixed hub.