Reading Churchill: Was the cavalry the stupider branch of the British Army?

Winston Churchill, writing in My Early Life, mentions how wealth affected one’s choice of branches in the British Army:

I qualified for a cavalry cadetship at Sandhurst. The competition for the infantry was keener, as life in the cavalry was so much more expensive. Those who were at the bottom of the list accordingly were offered the easier entry into the cavalry.

Tom again: So, by making the cavalry expensive, the wealthy aristocracy was able to reserve largely for itself job openings in part of the military — perhaps a place to store second sons without sufficient brains for other jobs? I asked Douglas Allen, an economic historian who has studied the political economy of the British military. He wrote back, "No doubt though, it took a long time for the aristocrats to be replaced by attrition, and they probably did use a price mechanism to keep the vulgar middle class out of their preferred positions."