Umbreon, I'd just take a quick glance at the Wiki to give you an idea of what they gave to Mewtwo:
http://www.ssbwiki.com/Mewtwo_(PM)
What it can't properly illustrate, are how significant some of the details are. Being able to attack + float from Teleports is wtfbbq good, improvements to tail attacks + ability to float means those tail attack buffs are further multiplied in usefulness, etc.
Most M2 weakness from before have been marginalized.
1. Vs. projectile spam he has a better reflector, better tail attacks for stuff he can clank with, floating above/around projectiles, teleporting at the user once the projectile is used and having meaningful options after the tele, etc
2. Any old reliance on WD back or Dtilt is usually not the case anymore. For spacings where he would like to consider those options to begin with, he has the additional option to float Aerials or combine teleports + floating/attacking.
3. His teleport spacing is still fairly predictable, but you are much less limited since Teleport lets you attack and float. It's the difference between the Melee version of G^W Upb, and the PM or Brawl version. Being able to attack, or further reposition after the teleport, opens up the door to flexibility that Melee M2 never could have obtained. Teleporting higher than you need to, and figuring out either a floating direction to help save you or an aerial that might help get back down, forces the opponent to cover more options/specific spacings from Tele.
4. They buffed his weight, and his recovery is even safer. His weight is in the 90's now, I'm pretty sure he's heavier than Marth now.
5. His platform game is something pretty sweet. Floating Uair basically ruins characters LOL, and people that shield will not enjoy 100% safe Nairs that come from below or weave around them. You could argue that some of his platform trapping options are weak to CC, and may give the opponent a chance to break out semi early, but you can usually vary your floated "attack" and instead waveland from the float to go for a grab, or use the massive Uair hitbox to hit them before they can tech, or just go for Nair.
Mewtwo is basically a prime candidate for getting some of his goodies taken away. The problem was that for every cool thing he got tacked on, nobody effectively tested how well the traits compliment each other. This was no easy task, and I don't put much hard blame on them for missing out on why the combination of his traits goes to a dark place. That's a ton of testing and speculation over how well he would do in Neutral. Mewtwo got buffed attacks, plus buffed mobility. Penalty flags should have been thrown up everywhere as if Terrell Owens just started a Touchdown Celebration.