My reason is probably the opposite of NJ.
I like the floatation of elk over deer hair. But, I don't care for the somewhat extreme flaring of elk hair.
I like the deer hair which is less flaring than the comparadun deer hair. At Blue Ribbon, they stock patches of deer hair marked "X-Caddis". This deer hair seems best suited for general caddis patterns. It doesn't flare too much.