There is no "best girl".
MrDots tried (imho successfull) to create all girls different to assure there is at least ONE for each taste.
There are Black, white, european, asian, redhead, blondes, black haired, long haired, curled haired, mature, young .........
So of course there should be one type you like and another type you maybe dislike - that's ok.
Me for my part, i dislike Yuki for example, even she is kind of cute - she is just not my type.
As there are thousands of players all over the world, Dots tries to match all ethnics and tastes. Of course this can't be done 100%, as we would need much more girls in there, but it's a try to do the best.
As a negative result, it may happen that you dislike more girls than you actually like, if you stick to one stereotype for your own - probably that's why so many players complain.
BUT:
As mentioned before several times, this game is NOT meant as HAREM game - just pick your favorite, and all is fine XD