Of the three brands mentioned I've generally found Stahlwille and Hazet to be superior to Gedore. All have their strengths and weaknesses, and I know Gedore have many supporters here, but some of their wrench patterns have a pretty poor finish, and I was very disappointed with some Gedore 1/4 drive I bought a few years back (very flimsy). Gedore's strong area seems to be the larger tools.
Stahlwille are superb all round. They make a wide range of tools including a lot of items geared towards the aerospace industry. Their strengths are their socket wrenches, together with their handles and accessories, which have unique flowing forms and are very practical to use. Likewise their regular wrenches, which are among my favourites. A major strength is their finish - it's a true satin (not matte that's called 'satin' by some others) which wears superbly well.
Hazet make lovely wrenches too. The patterns differ slightly from Stahlwille, as does the finish which is a part matte / part polished which also works superbly! Hazet offer superb socket wrenches and their strength seems to be their inhex/torx sockets. Their TiN coated bits are about the toughest out there and they are alone in offering two totally different styles of these, not to mention all the different lengths and specialist bits!
Personally, my Metric conventional box end wrenches, open enders and short combo wrenches are Stahlwille. My long combo wrenches, non offset box ends and flare nut wrenches are Hazet. I love it all - and I own a lot of Snap On (in A/F sizes) and old British Britool too!
maybe not the best by default (pick wisely)