I put my current favorite on a specific button on my hotbar, and I have two hotbars just for mounts so that when I'm feeling specific (I want to ride Kirin! I want to ride Rose Lanner!) I can just pull that one out.

But I totally feel this. I hit the aerial mount and get a chocobo more than 50% of the time, I swear, and I have 22 aerial mounts. Only 6 of those are chocobos...it's ridiculous.