Check out
Theater Monkey, a London site which has theater reviews and venue information. Specifically, Theater Monkey has seat maps for each venue which are color coded and offer an opinion about the relative value a seat compared to the view it provides. It's all subjective of course, but it might help you decide and compare.
Enjoy the show.
Barry
<sorry to repeat the essence of Dave's message -- I missed it when I read down the thread -- but I do concur about Theater Monkey >