In reply to Keiran.A:
The Cicerone guide covers more areas and routes, but it can sometimes be hard to work out where things are.
The Ground Up guide makes it easier to find things, and is good for the ego with its upgrades, but misses a lot out.
You need to buy both, and then realise that Welsh Winter conditions are fickle enough that you can end up going the whole season without using either of them.