GHK m4 over the we and tm any day. TM has possibly the worst gas efficiency and you have to remove part of the magazine for green gas to work properly. We is nowhere near as reliable as the GHK either
Check out: http://arniesairsoft.co.uk/forums/index.php?/topic/215433-ghk-m4-gbbr-105/
http://arniesairsoft.co.uk/forums/index.php?/topic/170736-we-gas-blow-back-m4a1-carbine/
http://arniesairsoft.co.uk/forums/index.php?/topic/215675-first-impressions-tokyo-marui-m4-mws-gbbr/