In my personal opinion:
Kira Kira > Deardrops > Edelweiss
I'm at classes so I can't explain in detail why, but. I'll do so later tonight Maybe I'm a little bit biased towards Kira Kira, since it was their first (readable in a coherent English) title that I read, but the reason why I liked it so much is because it was a great slice-of-life story abou how the characters managed to form a music band and stayed together in good and bad times. Also, Kirari Normal End is powerful stuff. That is all. Shame I forgot the last phrase of this one, since it is pretty badass and wanted to quote it (under spoilers, of course
) The only complain I have about this title is the art style; those ears, yikes.
Deardrops... It's pretty good, but it suffers from being a follow-up of Kira Kira, so comparisons are inevitable, especially since both titles deal with music, plus some of the routes are very weak (Still salty about Rimu's route being a trainwreck). Still, a very good title in its own merits, plus, the art is miles better than the former.
Edelweiss is a very good comedy game, but tbh, for me the characters were somewhat forgettable. Also, a recommendation: play both this one and the Fan-Disc, since it is essentially an expansion pack with two (three?) extra routes.