I realize to a gamer every ms of difference in ping times seems to matter. But looking at the big picture, those differences (including download/upload) cannot be treated as significant. It’s most likely the normal variability you can expect from your router and the internet at large.
But for the sake of argument, let’s assume those differences, while minor, are at least consistent. It could very well be that the handling of ethernet is slightly less efficient than wireless within the router, all other things being equal. We can’t just compare wired vs. wireless in the abstract. There’s real code involved, and each takes different paths through that code. And if all the other variables are closely matched, it might very well expose those differences in the router.
Regardless, I strongly suspect that in normal usage (i.e., w/ many other wired/wireless users), you will find wireless is NOT better than wire, if only because wireless is half-duplex. Only one wireless client at a time can communicate w/ the router; all others must wait their turn. Now those slight inefficiencies in ethernet don’t matter anymore. Ethernet ends up being the tortoise that eventually wins the race.