"Best m4" guides are pointless. There is too much ground to cover. You cannot simply skim over a two brands in one sentence. Many brands offer many different lines of guns, they are often completely different and suffer from completely different problems. You can do a writeup on how VFC SR16s have beautiful trades, but some of them had E series trades while others had the KAC trades. VFC external quality is different from their E series lines, KAC lines, Colt lines, VR lines, Socom Gear licensed lines like Noveske and DD... They're all different.
Another problem is that a fully detailed writeup on the pros and cons of each brand will become out of date and obsolete within a few months. For example you can say decent stuff about KA and CA, but when they relocated production from HK to China the quality dropped significantly.
Good job on the effort, but I don't think continuing this is worth the work it would take to maintain a detailed and accurate writeup.
Guardians of Asgaard - KF32
VFC H&K 416C
VFC KAC SR16 JL Billet SBR
TM FN Five-seveN