I'll back Sarah's view - Roclite 315's are excellent for most runs. As gucci says, don't expect comfort from Walshes, but the grip is awesome. I find my feet (particularly insteps) get hammered to bits if I have to run on stony ground in Walshes (this probably makes me a big wuss), but if you're only on the untracked fells, they're great.
After experimenting with both, I'm leaning towards Inov8, but I can see why folk like Walshes. They seem to be better-built too.