In reply to Scruffy:
If you are using the double rope correctly you should get benefit in nearly all Trad routes.
The rope drag is reduced, this makes a massive difference if you have gear off to the sides, which is common for Trad routes. This also means you are less likely to pull out gear through rope drag.
If you only have a single rope you can't really place two bits of gear from the same stance (same height) if they are not really close together as you will make the rope weave really badly. Often as you approach a crux you will want to play two pieces so this is a real problem.
If you fall while clipping the rope you still have the other rope without all that extra slack.
If you fall the swing is limited by having a rope each side of you.
There is redundancy in the case of a rope failure (eg sharp edge).
When setting your belay you can connect one rope to one piece of gear and the other to the second, avoiding having to equalise so many strands.
They are lighter than having to carry the same length of single rope. You are going to need that double length for abseils (eg 35m route, you would need a 80m single for the abseil but a pair of 40m half ropes is long enough and lighter).
Which of these applies to your crag?
Post edited at 20:44