I think Diva get reviewed a lot because of decent comms when booking and they keep their roster of in/active girls up to date.
To me, the only reason to use an agency is to make booking quick and easy - you can waste a LOT of time trying to arrange bookings with indies, and even end up empty-handed. With an agency, you have a guaranteed booking at the time you want in a matter of minutes. However, with some of the poorer agencies, you have no idea which of the girls on their web-site are actually working that day, and when you request a girl, they then phone back 15-20 minutes later saying that they have been unable to contact her, she is not actually working that day, she won't be available until x hours later, or such like. I see little point in using such agencies. In my experience, Diva are the best in this respect, they update their web-site daily as to who is working that day, and when you phone they usually have a good handle on who is actually available at the time you want.
The other thing to consider with agencies is how picky they are about the girls on their books. Admiral used to have about the largest "book" of all, purely because they would take just about any girl going (they appear to be far more selective now, following their change of ownership). Babylon likewise don't seem to be too picky - they are quite happy to keep listing girls that other agencies have dropped. Diva have a large book, but if you look at how their girls are listed, it seems to go alphabetically three times, in other words, they have three tiers of girls.
