go for the KO 2343
KO servos are the best in my opinion.
I want one of these but cant afford it yet!
with the other one needing 7.2 volts to run i think thats used for trucks or planes etc... KO 2343 are widely used in all touring cars. and this servo or the KO 2143 is on my next to buy list
KO 2143 is set and can not be programmed where as the 2343 can be programmed to be faster or slower. but max speed is .08 secs i believe which is set at default for 2143.
Hope this helps.
cheers