Here is a list of the differences in DSMBL as compared to DS:
-The scoring system is different in DSMBL - you have a cumulative multiplier (displayed underneath your item counter) that increases from 0 to a max of 100,000. In DS, your multiplier maxed at 10,000 but got reset every time you came out of Power Up mode. In DSMBL, your counter lowers by 30% every time you die (in DS it reset to zero with every death).
-The multiplier rapidly reduces (as in Mushi Futari, Ketsui, and others) during boss fights.
-You can now increase your item counter on bosses. To do this you must have your option be in contact with the boss. For Windia, Follett, Rosa, and Sakura, you need to tap shot (A or B) quickly to raise the counter. For Casper you just need to hold the laser. Follett increases the fastest with tapping, and actually it increases rather quickly if you just hold laser as well, so she is unique in this regard.
-Skull values are higher in DSMBL, and it's more beneficial to let all skulls fall and break, whether in normal or power up mode. Skulls in Power up mode add more to your counter (double?) compared to skulls in normal mode.
-you get skulls when you cross 500 on the counter from enemies that previously didn't drop skulls (and never drop skulls in DS).
-you suck in skulls a lot easier, with a wider "suck in" range
-When you power up at 1000, your shot is about twice as strong (you can see this clearly with Windia, as her sickles are twice as big in power up mode triggered at 1000 as compared to normal mode or a power-up triggered at 500-999). You also get a burst of large gold crowns. When you power up at 500, your shot is of normal strength.
-When you power-up at 500-999, your counter starts counting down from 500.
-You don't get full gold crowns from enemies until you max the counter at 100,000. In DS, you got full gold crowns when you maxed at 10,000.
-Some of the colors look brighter, and some of the bullets have a pinkish hue, instead of the pure purple of DS
-suicide bullets (the little stars) no longer add to your item counter, nor to your score (well, they add 100 pts each, but that's not much). They convert to skulls during the transition from normal to power up mode.
-A new stage was added, the Ice Palace.
-A new difficulty was added for each stage - rank level 999. The backgrounds turn dark in the stages when you select this rank. If you do all rank 999, then the Ice Palace is also in rank 999 (and the background is dark).
-A new character, Sakura, is playable.
-Boss patterns were tweaked, for example the Forest boss's final attack on rank 3 is very difficult to dodge now, while it is comparatively simple in DS.
-Bosses emit suicide bullets when you enter death mode (play 5 stages at all rank 3, and the fifth (and all subsequent stages) will be in "death mode").
-The characters seem to be slightly rebalanced - Windia is beefed up a bit and Rosa is slightly toned down. Overall it all feels better balanced compared to DS.