Tm MWS has a massive amount of aftermarket support (though not all of it I would consider an upgrade) but enough users and support to see you until you retire from the hobby
GHK QC has recently (2020 onwards) slowly deteriorated, “apparently” their tooling is wearing out so machine tolerances mare slowly getting worse
Their AK version is slated for out of line trunions and squint barrels
Though, to be honest, my pre ‘19 v1 M4 is superb with a couple of thoughtful upgrades. Parts are easily enough found from HK retailers
I can’t really comment on the MP7, other than it is roughly 10% smaller in size than the RS version
(rumour has it they copied the blueprint of the genuine item but not to scale 😂)