I thought the OP would say something intelligent. <<
I guess I'll do that.
Snake has like at least 6 matchups that are out of his favor (DDD, Falco, Pikachu, R.O.B., ICs, Wolf), while MK has only one or two matchups out of his favor (Snake, and G&W). MK is clearly the better character. Oh, but reasons why Snake sucks.
Snake has a bad air game, an easily spiked recovery (which many characters can set up into easily), moves slowly without his mortar slide, and the moving slowly part is an issue because he is very bad at dealing with other projectile spam. Also he has only ONE reliable kill move (U-tilt), whereas MK has at least three (D-smash, Up-B, D-air, maybe glide attack).
And by reliable, just keep in mind that I mean a kill move that you can land consistently, that isn't going to be totally wrecked by diminishing returns or being ultra telegraphed or unsafe on block/dodge. Snake's F-tilt and Jab for example are NOT reliable kill moves because Snake does better using these attacks for damage dealing. Snake cannot use his aerials often as kill moves because if he completely whiffs them, then he will be punished. His explosives are all situational. Yeah.
Matchups
DDD: CG ***** Snake. No further explanation is needed.
Falco: laser camping destroys mortar slide. Chaingrab easily sets up into a spike.
Pikachu: CG lameness, Thunder Jolts, Thunder ledgeguard, oh my.
R.O.B.: Lazor camping and Smashes which beat the mortar slide IIRC. Plus R.O.B. is just too good at ledgeguarding
ICs: Ice blocks stop the Mortar slide. Chaingrab needs no further explanation.
Wolf: OMG LASER CAMPING. D-throw and then spike Snake.
And besides, Forte's Bowser beat Chillindude's Snake. Like seriously wtf...