Pictochat can be a good stage vs MK. However, the sides are close, meaning it's easier for him to SL you off as you recover or Dsmash kill.
Also, MK is one of the few characters that can punish stone on reaction, making even infinite stone unsafe in a lot of cases if they know about it.
That being said, MK is generally as good or better than us on most stages.
Brinstar is a bad idea due to the fact he can SL cancel through the ground into a Dsmash, and the sides are really close.
Delfino is a MK CP.
LM is fairly bad since we have nothing really abusable on that stage, whereas he does, even if it's kind of sub-par for exploits on that stage.
PS1 is pretty good. We have more exploits, and the infinite stone glitch is close enough to the ground that he can't punish it with SL.
PTAD isn't too great for the same reasons as Brinstar, and because he can abuse the same things as us.
I personally don't mind any of the neutrals, but BF is supposed to be really good for him.
Japes is a decent stage against him, but he still does better. It kind of negates his recovery advantage, but it doesn't really hurt him either, and he has some cool exploits on this stage. Also, he's more likely to kill off the sides, so the high ceiling actually hurts us more than him, since we have more vertical kill options.
He's better than us on RC too.
We do pretty good on Lylat. The tilting ground can mess him up a bit when he recovers, he can be Ninjaspiked, however unlikely that may be, and the platforms don't really help him any more than they help us.
Castle siege doesn't really do much for either of us to my knowledge. Only thing I can think of is the statues allowing move refreshing to us both.
Frigate isn't bad either, but there isn't much that we can do there that he can't, other than the grab release thing against the wall.
Halberd is bad, M'kay? Autocanceled SLs though the ground will be bad for your health, as will the inevitable gimps.
Norfair is also bad. Bring him there if you want to get planked for an entire match.
I don't know what to think of Pirate Ship... In theory, it'll help us more than him, but it's a pretty meh stage for us both.
I don't know enough about PS2 to talk about it.
Same for Distant Planet, though MK's glide toss and autocanceled SL could make this stage bad.
Basically, for this matchup, I'd stick to neutrals (especially SV), Lylat, or PS1.
EDIT: Rofl, as I said before, if you want to discuss that (I still definitely disagree for numerous reasons), bring it to the general chat thread or xat chat. Hell even the matchup thread if you want.
. Basically what fromundaman said on the previous page, but I dunno about Pirate Ship though...I generally seem to forget that that stage exists.