I'd probably say Gogeta wins, since even with the implications of powerscaling in Super, Goku doesn't need to end up much higher than his Beyond Limits SS4 self. Even feat-wise, he doesn't necessarily need to be leagues above GT, considering that the difference needed to reach different tiers of power such as Solar System level to Galaxy level to Universe level doesn't need to be realistic battle power-wise, since even a difference of ~300 or so was enough of a gap to go from normal human to Island level by battle power logic.
SSJ Goku wrecks though imo.