If it was a choice between the two I'd pick the Hazet. I've got a few Gedore tools I've picked up over the years, they're o.k. but not top end. Some of the wrenches have quite a rough finish. I bought a 1/4 inch drive ratchet , sliding t, sockets and extensions a couple of years back and they were finished o.k. but were fairly lightly built compared to others, and didn't fit together very rigidly. A couple of guys I work with have said Gedore are much better at making the bigger stuff! Maybe?
I havn't got much Hazet, only a couple of larger wrenches and a socket set I keep on my car, but it's all top end, really solid, and I'd buy more! Very consistently finished too, the wrenches I got are almost identical to ones my Dad got 30 years ago!
Agree with previous poster though, I'd probably prefer Stahlwille overall. I've got a fair amount of that and it's great. Satin finished, rather than the matt and polished of the Hazet, and equally tough! Doubt you'll be disappointed with either!