depends on the terrain and the temeprature.
Flatter it is, colder it is, the better a TB will be. TB's are a dime a dozen in my area, thinking of getting one to try. My GF rides LD's on a TB If she conditioned him half as much as I condition my walker she could be a contender in Southeast winter LD's.. He is about even unconditioned as my Walker mare is right now. I used to be able to outrun him but he is getting better. If he wasnt so dang mean I might ride him.
You get in hot weather and lots of climbs and rocks, the shorter more nimble arabians are pretty much it.