In reply to Michael Gordon:
> Maybe a bit more like a ground-up (though still not) if it's a bold route. But consider a well protected crackline which someone leads resting every metre or two, before going back and doing it clean. There is next to no difference between this and having a play on a top rope before a clean ascent.
> On a steep pumpy route, being able to rest as long as you like after a fall then start again from halfway up will be much easier than having to start leading again from the base, with the uncertainty of the hard moves you previously failed on still very much intact.
But does the uncertainty actually make much difference if it's a steep, well-protected crack line? You can just keep trying it until you get it, on gear that you've already tested, it's just a bit slower and more faffy because you have to untie and pull the rope and retie and climb back up every time. In this case, I'd say that dogging it to the top, having your mate second it, and then going at it again placing all your gear on lead to get a clean ascent is probably actually harder than lowering off and pulling the rope, since you don't have the luxury of pre-placed gear to save you energy.