I've had bad experience with EXI, too. Went thru three D227s within a month. What Syco said about vehicle weight IS true. If your 1/12 car is less than 3lbs, you could get by with a cheap servo. But much more than that, you'd probably want to go with Hitec and metal gears. (Although I had a 645MG crap out in my 4.5lb truggy. Very suprised about that. Ended up getting a $50 Hitec servo for the truggy.) But I still run a $15 servo in my Evader, which only weighs 3.5lbs.
Lot's of guys run Savox servos, but from what I've read, they require an External BEC because of the amps they draw...they tend to "brown-out" some BECs. My LHS won't even carry them. Too expensive and too many problems caused when people install them.