A while back I attended a race clinic hosted by Ryan Lutz and Joe Bornhorst... one of the topics of discussion was selecting a proper servo.
For starters they recommend selecting a brand that offers replacement gear sets as a bare minimum, and if budget allows, consider aluminum case servos or at least a brand that sells replacement cases should you tear a mounting tab in a nasty crash. Metal gears are a must, with titanium being a pinch more durable than steel in general. They also said everyone's reaction time is different and most folks should select a speed somewhere between 0.08 - 0.12 sec/60° and then use the "steering speed" feature on the radio to dial back the servo speed for your desired reaction time.
It's a good idea to first look at setup sheets to see what size servos folks are using for the class you plan to race... i.e. get a lighter low profile servo is less weight up front is desired (typically used in stock classes) or select a heavier standard servo with full aluminum case to add more weight up front to get more steering response. There is no single right/wrong answer, just a bunch of variables to consider when making your selection.
If it were me, I'd probably go with the
EcoPower WP120T just to start out with,
replacement gear sets and
servo cases are very reasonably priced for those who require buying from a US retailer with a reputable 1 year warranty.
If you are willing to restrict yourself to a 30 day warranty, then consider the OEM for the EcoPower 120T which is the
JX CLS5830HV who is distributed through RC Juice. The replacement gear sets are 100% compatible between both servos.
If you want the same servo enclosed in a solid aluminum case then consider the
JX HV7232MG servo
Higher quality servos discussed here