Should I have said an asian and a caucasian? As I said, the races in TES are more cultural distinctions (i.e. nationalities) than they are biological ones. There are Khajiit who look just like humans, and Khajiit who look just like housecats. Both types can theoretically mate with Imperials. The Imperials are really a catch-all term for at least 2 (but morel like 22) different peoples. Since we can now choose how fat or skinny we can be, does it make sense that a fat Khajiit can outrun an athletic Breton? Not to me it doesn't.
Race does have little do with it, but there are biological differences between these races. A heavy khajiit will run slower than a light Bosmer, but if the khajiit trained himself then he will be much faster than the bosmer, because he has a biological edge with running. Biologically speaking, a Neanderthal would run faster than a Java Hobbit, but an early man would run faster than both, but there are environment and individual health factors that can obviously come into play.
In game, it could work like this:
You pick a race:
Khajiit- 20 Speed
Bosmer - 13 speed
By default, a Khajiit will run much faster than a Bosmer. But if you add things to that:
A Heavy Khajiit wearing heavy armour: 13 speed
A lean Bosmer wearing enchanted light armour - 19 speed
You have now thrown in several factors that make the Bosmer somewhat faster than a khajiit. Now give the cat a big meal and a lot of wine, he will then become a slow, stumbling moron with the speed of 9.