RE-01R's are the most popular at this point, probably having a lot to do with Bridgestone contingency. Some are trying out the new Toyo R1R, but despite the contingency offering there not too many seem happy with the results.
The next possible ST* "tire to have" looks to be the Dunlop Direzza Sport Z1. Not a ton of availability at the moment, but all sizes should be available by the end of April. Should be another top tire to consider.
As for myself, I went with the Bridestone RE-01R due to their significant support of the sport last year, contingency, and the fact that it's a known quantity at this point. In 245/40/17 though of course.
FYI, a test by Tire Rack
The contenders:
-> Bridgestone Potenza RE-01R
-> Yokohama ADVAN Neova AD07
-> BFGoodrich g-Force T/A KD
-> Dunlop Direzza Sport Z1
Overall Test Results: Dunlop Direzza Sport Z1 Ride & Drive Review
Individual Test Results: Dunlop Direzza Sport Z1 Ride & Drive Review
