VFC & TM are the most recommended brands for gbb ARs.
VFC advantages:
-excellent gas efficiency
-durable steel FCG/BCG
-Strong recoil
-real spec parts
-Decent accuracy ootb
-High gas capacity
VFC disadvantages:
-Expensive/uncommon in the UK
-Little airsoft specific aftermarket
TM advantages:
-Very strong airsoft aftermarket
-Excellent efficiency and cold weather performance
-Decent gas capacity
-High ROF
-Good accuracy ootb
-Materials design around their limitations
-1/3 cheaper than VFC
TM disadvantages:
-Unrealistic/toy-like design & action
-Mostly zinc alloy
-short inner barrel, low fps
-Aeg spec parts
WE system is no longer recommend because their design have basically no advantages over the aforementioned brands beside being cheap. Even then there's better alternative(double eagle mws clones).
WE:
-Infamous cheese zinc alloy construction
-unrealistic internal design
-poor winter performance
-poor accuracy
-Little aftermarket (besides ra tech)
-Bolt lock failure
-unappealing externals(steel parts stand out from alloy)
As mentioned, double eagle mws clones are best bang for your buck since it's a direct clone of the mws with steel internals while being cheaper than a TM mws. The N4 and Ghetto blaster are both recommendable. However you may need to shim the magwell and replace the nozzle.