In reply to Paul Hy:
On virtually any grit venue under 25m (ie nearly all of it) or where the belays are not well back, as a grit guidebook worker, I've only used one rope folded up in the last 20 years. Usually a 60m but on short crags sometimes a 40m and typically around 9mm to give it longevity. Even where belays are well back I usually take my 40m and preset a belay at the top (and climb on a folded up 60). Why carry two ropes unless you are training? The advice of cutting a rope is to be avoided (the only ropes I ever cut were damaged) as is the advice for thin half ropes (grit is unforgiving). My Genesis ropes have lasted yonks. If you are unlucky enough to need lowering off a bigger grit crag from above 15m set up a hanging belay and pull the other end up.
Edit... some routes with bold traverses are a lot safer with two belayers (Wuthering is a good example) ...so two ropes are handy there for a three rope system (one folded as per normal the other off to the side..with belayer tied down.. to protect against a swing)
Post edited at 10:03