What are you talking about? Keshiks are better than camel archers in almost every respect. They move faster, they gain levels faster, they generate great generals faster, and they can move after attacking just like camel archers. The only advantage camel archers have over keshiks is that they have a slightly higher ranged attack value. From a strictly military perspective, there's no contest; Mongolia is way better.
Of course, that amazing unit is pretty much the only thing you get with Mongolia. (Well... that & the khan that travels along with them.) With Arabia you get all sorts of nifty economic advantages. Plus the desert start bias.
Now you say slightly higher ranged attack value.
Keshiks are 15 16
Camels are 17 21
Thats roughly 33% more ranged strength for the Camels, i wouldnt call that slightly... Its a bigger jump than say longswords to musketmen.
I´ll take the Camels any day over keshiks