In reply to andyd1970:
Don't know about the Saucony's, but I've got both the Hokas you're looking at.
The Challenger 4 I use as a road/light-trail combo shoe, it's very comfortable, but I think it has it's limitations on rough trails and any depth of mud. The Speedgoat 2 I use on rougher trail ultras, and absolutely love it for that terrain.
The Speedgoat feels fine on roads as well, so if you're likely to be just buying one, then I'd base decision on how rough the trails are you plan to run on.
I wouldn't really use either as a mountain shoe though, you really want something with deeper lugs and a bit lower to the ground - I'm currently using Inov8 X-Claw 275 which I'd have no hesitation in recommending.