I've thought if I did a world tour with long stretches through non-advanced-bike areas like Mongolia or such, I'd want discs but with V-brake posts at least on the front fork, and capable rims, just in case. This might also influence decision for hydraulics on the discs or not, as with not, I could just reroute the cable, whereas with hydro, I'd need to have separate cables for the V-brake. I know they briefly make hydraulic rim calipers, but I'd prefer to not do hydraulic line open-heart-bypass in the middle of nowhere.