For outright best, it's hard to beat the Futaba BLS series. They'll last damn near forever, are smooth as butter and because they respond to signal input so fast, you can more or less disregard their actual speed specs and know that they'll be faster than you may even want when in the car. I've ran a BLS451 in a buggy, stadium truck and SC truck and it's been the best servo I've ever owned in all of those applications.

If you're on a budget, the Savox line offers good value for the money these days.

Unless you like your car to make a buzzing noise constantly and enjoy changing broken servos often, stay away from Chinese un-brands with too-good to be true specs and way too good to be truly quality pricing that are usually sold on either Ebay or websites with grammar than should, by itself, tip you off.