Had the TM mp7 for about 6 years now, by far my most favourite gun and the most reliable, used it hot and cold and once the mag base plates have been sealed its been flawless other than a hop rubber change in all that time, run it on abbey sniper gas most of the time, used .28s and never had a problem, a lot of guys say the nozzle is prone to breaking but i seem to have gotten one that refuses to break?
cant comment much on the umarex/vfc one too much, had hands on with the new gen AEG and wasn't majorly impressed with the exterior looks (the TM finish felt much better) though the guy using it thought quite highly of its performance.