they both run at the same speed. on a program that utilizes 6 mores the 1090t would win.
but very few games use 6 cores. so in most games they would have near the exact same performance.
so in gaming your looking at pretty much the exact same performance the thing it would come down to is which you could oc more.
until more games whit hex core support are released it will be the same but when hex core support is available the 1090t will win.
no point in extra cores if there not used. gaming on pc has only just started adding mainstream support for dual cores so it could be a while for hex cores