Obj 777II or K-91? Or just Wait?

DeviouslyCursed: Win Rate stat wise on the NA server: Char, AE, and 777 are all about the same and toward the top of tier 9. Then there is a big gap and the Kunze which is middle of tier 9. Then another big gap and the K91, which is one of the worst tier 9's in the game (NA server). For EU and RU servers, the difference isn't as big and both the Kunze and K91 do better than they do on NA server, but the order stays the same. K91 is always last of the 5 reward tanks. On RU server the Kunze is almost up with the Char/AE/777, and the K91 is middle of tier 9's.