Well it would be better to decide your requirements first.
This is what i decided on while contemplating a new servo for my XXT:
1. 10kg-cm / 138oz-in
2. 0.13 - 0.17 sec/60*
3. 50 gms weight
4. Digital
5. Metal Gear
6. Dust/Water proof
7. 2 ball bearings
8. Physical dimension
Similarly once you decide on the above we can start searching