Def Fox first. His MUs are more noteworthy. For one, Fox at least
beats DDD.
Fox loses hard to ICs, Pika, and Sheik. The former being top threats in today's metagame.
While DDD is an obstacle, Wolf goes fairly even with most of top tier (ICs, Marth, Falco, Diddy, Olimar, & Snake (-1)). Pika is an overrated -2 that most Wolf's would agree isn't so bad, the CG is a pain but it can be avoided with things like Platform camping, Counterpicks, ect ect. I personally believe Wario isn't as bad for Wolf as most say, if we were to include .5s like it was discussed earlier, i'd probably call the MU a -1.5 for Wolf. That one's opinion though.
With the whole "few players can use Fox effectively" statement, that's true to an extent and I do agree, but Wolf is a very underdevoloped character and has lot's of potential that's only just starting to come out. Wolf consistantly pulls in results (See:
Kain @ Vengeance), and has always been a character who could hold his own. His main drawback is what Ish was talking about I don't know how many pages ago, he doesn't really
beat any top threats. On the flipside, he doesn't lose to them either, and going even with two of the most predominate threats (ICs & Olimar) only helps his case. I'm not saying Wolf is game-breaking or anything, but he's worked for a High tier spot and compared to his Mid tier brethren I think he deserves it the most.
Seagull may want him to stay Mid so he can **** Mid tier events, but I believe Wolf has it in him to make High. I wouldn't mind King of Mid tier though, for stated reasons.
EDIT
A tier between high and mid probably would be perfect, Ish.