Seasons 6-7 aren't that bad, they each have a decent number of good episodes. They definitely each have a few that are kind of boring or dumb, but as a whole the seasons aren't as terrible as some make them out to be.
I love both franchises, but I have to give Mario the edge. I prefer the classic Sega Genesis Sonic games over the classic Mario games, but Mario has better games overall.
I really want to play Super Mario Odyssey but I'm too broke to afford a Switch at the moment. =/