it may be both. tell us what you have now.

High speed servos are always good to have and the radio response is also important.

I use JR821 for most of my on road cars except my TA05R which I spent a bit more on and got the hs-5965mg servo. I use futaba 9452 or ace 1015 in my off road buggies/trucks.

but... lol... i still have a futaba 3003 in my tamiya M04L.