Magical Drop II without a doubt. Pulstar is a very pretty game, with cool tunes, enemies and explosions, the whole nine yards. But it is harder than anything you've probably ever played before too. I love shooters to death, and a challenge is always welcome, but Pulstar is more memorization than anything else. Too strict, not enough room for experimentation or, God forbid, error. That's right, you lose them power-ups later in the game and you can kiss any further progress good bye.
Magical Drop II on the other hand is total addiction. Fun as can be, cool characters, dead-on gameplay, great soundtrack, I'm hard-pressed to think of too many negative things to say about it. That, and it's got serious points going for it when it comes to replay and tournaments with your friends. Get it man, you'll love it.