I honestly thought that M2Y was a pre-evolution of M2 the first time I saw it (just the picture, not the explanation of Mega Evolutions), almost like the bridge between M and M2.
M2X is just... I don't know, there's just something about it that makes it feel like a very boring Mega Evolution. Almost like what Mega Venusaur is: "Wut? It looks the sam- Oh, it gets an extra flower. OMG, ITS GOTS VINES TOO!" Compared to something like, even Mega Blastoise where it gets hand cannons and one gigantic cannon on its shell... or Mega Mawile where it gets an updated outfit and a second fake head.
M2X looks like M2 ribbed with Shoulderpads. M2Y is the Mega evolution that has the biggest visual different over the original.
.: Cube World :: <>====|=<(>o<)[__] @>~~ o===<(>o<) :. .: You gotta be can we do you think if we can make a should just be alone? :.