I am notFutabatec support but you may find some help here ->
http://servocity.com/html/futaba_servos.html When I find myself faced with the same questions you pose, I check out the stats, performance and price here for what seems like a good fit for my next project.
As you look at the information, I always keep the Futaba 9252 in mind. At $75.00 with 92 in/oz of torque and speed of .14 sec/60deg they are my datum point. Add a bulletproof reputation and digital performance and they are what I personally compare all other servos to. Using the 9252 as a starting point you will find faster/slower, torquier/weaker, cheaper/more expensive servos but they will always look pretty good.
Hope this helps,
Bill