I think MP3 > MP2. Echoes has its moments but 3/4 of its environments are usually visually dull. The Temple Grounds is mostly a desert. Agon Wastes is another desert. Torvus Bog is a gray, nasty swamp. And all the while you're watching a repetitious cutscene hopping to and from a world that is poisonous to navigate.
I still like it overall and even 100%ed it, but I did find it pretty tedious at points.
Conversely I think MP3 is underrated. The game just feels fun to play, with great pacing and much more beautiful areas. I feel like everyone thinks of the chatter-heavy opening hour and forgets the varied, natural beauty of Bryyo, the imposing mechanical Pirate Homeworld, and the lusciously steampunk skyland of Elysia. I also preferred the stacking beams, the motion controls, the lasso, and that spooky derelict ship. Plus we finally get some Mother Brain. Corruption is just a good time.