I have the KO 2143 and it's a great servo. Before that I had a JR something-or-other and was also very happy with it. Previous to the JR, I went through several Hitec 925MGBB's before figuring out that Hitec servos just aren't worth the time or money. They lose their center oh-so-easily, and you start to think it's something wrong with your car.
If you stick with the top brands such as Futaba, Airtronics, KO, and JR you should be able to get a great servo that will last several years at least.