my (SAE) combination set is split roughly half and half between wright tool "wrightgrip" wrenches and williams "supercombo" wrenches. i like both products equally... i would say in general the supercombos have thicker handles (which are nice to hold but makes the tool feel a bit heavier), the satin finish on the wrightgrips is nicer, the implementation of the general "flank drive" concept on the wrightgrips is a lot more aggressive than on the supercombos, both makes are robust, fine, domestically manufactured tools that will last a lifetime if taken care of. i'd recommend either one... i haven't looked but i have a feeling that you could probably find the williams cheaper than the wrights on ebay or something. i don't have any stahlwille so i can't comment on that. fwiw my metric set is stocked with wrightgrips and old NOS bonneys, actually, and again, both great tools, but for some reason the bonneys are almost my favorite (personal preference). maybe consider proto as well, another good USA make, i haven't used a proto wrench personally so can't comment (but i like their ratchets and sockets). proto stuff seems available on ebay for what seems like crazy cheap to me. but anyway, all this rambling, tl,dr: if i were you i'd go for the williams, the quality is great, i'm sure every bit the equal of the stahlwille, it's got at least a mild implementation of the "flank drive" concept (if you like that sort of thing; i think it's cool; please correct me if the stahlwille has similar design; from pics i've seen, i don't think so), and it's like 75% of the cost. who can argue with that?
edit (i just keep going...): and you do not need to drop major coin to get a real nice set of wrenches. the metric set i mention before, i started out as a 12-piece set buying piecemeal from epstein's, for $97.85 (6mm-19mm, skipping 18mm). i'm sure their order fulfillment dept. hated it because it took them like three days to fill my order, LOL, but money's money, no?

i filled in later an 18 and a 20 and i'm still at like $125 for 14 pieces. if you're willing to put in a few hours and scrounge you can save a lot of dough versus a single manufacturer pre-made set.