I say there's no point in arguing the difference. As I've mentioned before, while the engine and name are both the same, they are two very, very different experiences. I like both equally. Each has their pros and cons. I'd have to lean slightly towards the sequel for being refined... buuuut...
One major ***** I have about the sequel is them trimming 100% of the excess. I can't stand their philosophy of streamlining crap so much that it starts affecting the levels. You can't deviate from the small, specific path they set out for you. There's 0 exploration. Many of the levels feel like going through an automated carwash at a gas station and a lot are incredibly short. There's no depth, it feels like. It's mostly just thin walkways to the next launch star with a node or two inbetween until you get to the power star. Beat Block Galaxy is a prime example of what I'm talking about.
Yeah! That's what it feels like. It's like minigame stations. Start the level, solve the puzzle/whatever in a small area which uncovers the launch star, fly to the next station, complete the minigame, fly to the next station-- and so on and so on.
When they first announced the sequel, I thought all right! They'll surely flesh out from the original more! Maybe we'll see Bob-Omb Battlefield-size levels AND planetoids all packed into ginormous levels! Lol nope.