All dependent on bloodlines and graft...
And for me, with lurchers, graft wins hands down. I'd rather take a pup off a dog that i know has been grafted hard at 3 year old, than one from a dog thats say 7 and though worked steadily, has hardly been pushed.
Point of fact for me, is who is on the other end of the lead... Mad keen owners don't keep shite, they can't afford to...