As it stands, there really isn't more than a vanity's worth of marginal difference really possible for mounts. Assuming we can even vary in terms of speed vs. treasure-hunting ability vs. mount inventory capacity, these will still be totally individual decisions based primarily on a player's grinding preferences. For a simple example, Gatherers with short log-in times will want the increased treasure-hunting ability so they can make a quick gathering sweep without having to think about node probability or routes. Those who have figured out the routes can take the little extra time with reduced treasure-hunting ability, but return to town less often with a increased inventory capacity. Those specializing in hunting truly rare, distant items, and know how and where to find them will go with the increased speed. Quest-levelers will probably go for increased capacity unless they want to be able to easily find treasure while in the course of hub-hopping. Vendor-all-but-my-best-equipment guys will go for speed. And that, for better or worse, fits the style of the game thus far.
We don't have any active sprint functions, and none at all for our mount. Our jump is non-variable. We don't have mount endurance mechanics. They don't have pain tolerance variables (to avoid bucking). Any armor they get will likely be more stat-based than anything actually useful to a cavalry rush. It does not appear that we will be doing any dual-mounted/unmounted divisional strikes on Imperial camps or armies in the near future. [Ahh, jeesh, just imagine the supply-stealing [via treasure finding], active event item-weight mount carrying capacity [based on what would normally be slot-based carrying capacity], the decoy running [using the speediest chocos], the trampling, the Chocobos tanking or making charge rushes while their riders are dismounted and supporting/leading the attacks... Seems I've gotten carried away.]