One thing I took note of right away was the long intro cut-scene. The game sets up its story in a nice, neat fashion and instantly sucks you in

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Then we get to the core gameplay, which is Legends 1 but far more refined. Mega Man has a lock on that works closer to say.....a Hyrule Warrior, being able to move left & right as he fire's his Mega Buster.
Mega Man also has his high-jump ability from Legends 1 too, with other iconic abilities like his rocket skates, drill arm and so on returning when you gather enough items.
So, the core gameplay mirrors Legends 1, with one interesting thing to take note; a exploit in the combat system. If you press Up while shooting rapidly (Locked On or not), you can fire far faster bullets compared to normal. Very, very useful for fights XD!
Anyway the presentation of the game is very impressive, with detailed character models, strong texture work and a soundtrack that really took me by surprise! I posted a few tracks in the OP if you guys want to hear them. But very good stuff, mixing the atmospheric tunes from the original game alongside really strong melody's.
Dungeons are designed more like Zelda Temples compared to the labyrinths in Legends 1, with a full on map system, map item and boss key item. They are also themed like in Zelda too, making them have more personality.
Overall, really love my time with Legends 2 and I can't wait to play more!
Regarding how each version runs, I can comment with the following:
-PS3: Runs great with a smooth frame rate and tight control system.
-PS Vita: Runs great and a big improvement over Legends 1 on Vita (no more slowdown, issues with cut-scenes and the like). Controls work great with no re-mapping outside of maybe the Lock-On being pushed to one of the trigger buttons