+1 for V710's. its amazing how long they last, considering their grip. I cant speak for track, but they will easily last 2x as long as a6's in autocross, without being too much slower. they still take wins at nationals, altho not many (their contingency sucks, so that doesnt help). others who have driven both say that the a6 actually falls off worse than the 710's in the tail end of their life as well. 710's are also much easier+cheaper to find used. just about no used a6 is worth buying.
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