Lemon wall alert.
So, the company wars, the battle for the title of the blue mascot, how does it goes overall? Pretty even-ish, but with the Bomber getting some goodies over the Spinner.
The first thing to note here is that Mega is unique in the overall fighting style agaisn't Sonic because we do NOT have to guess as badly as others characters to catch Sonic into his spindash, lemons and disjointeds are two things we have that cover his main approaches, Air Shooter covering some "mindgames" trying to jump over our lemons in the bait.
But! Not everything is bright and easy for the Blue robot, if Sonic gets in, you'll eat some big punish because of his combo options, but do not be too afraid, since when it comes to the killing part, it's probably the part where everything gets bright for Mega.
Sonic does NOT have a reliable kill option agaisn't Mega, at all. We do not EVER have to be in the range of his FSmash, his USmash is slow, and the rest of his options are pretty obvious overall. While we have some pretty good momemtum breaker inputs (USmash, Air Shooter, Slash Claw, etc). But if the Mega gets caught and dies first, the battle'll become an uphill fight, VERY difficult to come back from, be worried about that.
It's actually how I would think a MM/Sonic fight would be, Mega Man has the sturdyness and with enough time he can beat the outstanding speed of Sonic, but you do NOT want to get confident, since that hedgehog does indeed have the tools to take him out first if not careful.
55:45
Ps: Lylat or Castle Siege are good stage options agaisn't MM, in case you want to CP him.