eh, I'm not overly familiar with them but I'll take a stab.
SF (ignoring MC) is mostly a mix of traditional mid-western USA workwear and vintage style clothes, with a more recent bend towards minimalist high end designer-wear, often asian, etc. It's mostly about slim trim fits and textures, etc. SuFu is a bit more like the latter part of SF, probably edging more over to the runway/fashiony side of things, I'd say it's more trendy small designer wear stuff, where SF still has some MC influence in there. Hypebeast tends to be about very over-the-top, if I may say somewhat obnoxious items, typically random mixes of bright colored shoes, large logos, somewhat baggy fits, more of an urban street look, but at times with rather expensive items. There's also a strong interest in retro and vintage wear, but where SF is more about the chucks and common projects, Hypebeast is more about vintage nikes and new balance.
at least based on visiting each of the sites a few times... that's my general impression.
(and yes, I'm sure someone will quote me and make fun of it and say I'm way off base without giving a better explanation)