I think it's pretty hard to rate agencies because there are a lot of things that are outside of their control. For the most part, until they get feedback from clients, they don't really know how good a girl is going to turn out. It's not like they require auditions
Also, the same girls occasionally move from one to the other, so the difference is not as large to me as some previous posters have suggested. That said, ALLD does skew a little more Korean than the others, and Candyland skews a bit more mainland Chinese.
That said, I would rank them:
1) ALLD - ALLD as an agency seems very responsive to feedback and over time has improved enormously. Great mix of younger girls and more service oriented ones. I also think they try hardest to be honest and accurate in their descriptions (except for the age deflation that everyone participates in). After a couple of tries I stopped seeing their Korean ladies because I think they are more conservative on average, but I have had a great time otherwise. I've had by far the best conversations with ALLD girls.
More than one girl has told me they like ALLD as an agent/employer more than usual, and I figure if the girls are happier, I will end up happier.
They don't seem to be super diligent about keeping their web site up-to-date, which can occasionally be annoying. They could use a better photographer too.
2) Moonbay - The girls I've seen at Moonbay were pretty and on the younger side. Moonbay is customer service oriented too, although to me they are slightly less so than ALLD. I find the girls here to be a little cookie cutter.
Phone guy for Moonbay sounds a lot like phone guy for ALLD to me as well.
3) Candyland - I have had good times with girls from Candyland in the past, but currently they don't seem as customer friendly as the newer agencies. The descriptions don't really seem to match up at all with what I experience in my sessions so the pictures are all I have to go on.
All three have clean and upscale locations downtown. ALLD also has a westend site.
All three have real photos of the girls generally, but I think Candyland is the best at choosing more flattering photos when required.