I haven't matched my rainbow total from Nutaku yet (28) but so far I have 11 rainbows without spending real life money. All of my DMM rainbows have bloomed forms available though so I'm not stuck with, say, evolved Flowering Peach and X-Mas Stewartia like I am on Nutaku.

All told, even with fewer rainbows on DMM my total power after five months is only around 32000 points lower than what it took me three years to reach on the Nutaku version.