I guess im the only one here leaning towards the sentry! haha Ive had mine for about 3 months, shot maybe 20,000 rnds thru it and its still working fine. I guess my favorite part of my gun is the rate of fire. it will fu#*ing blow your mind. it just shoots so insanely fast. to give you an idea, look up a g&p defender firing test (reddragonairsoft.net) has a good one, that gun is pulling an m120 i beleive. the sentry has an m100. so its just insane with my 9.6 and 10.8 volt batteries. im not sure what the exact numbers are but if the defender is 28 bbs per seccond, the sentry is about 36 or 37 bps. i own 2 kwa's with the 2gx gearbox aaand they seem to be smoother.....but i guess im a sucker for the magpul body, sweet rail, king arms rear sight, and suuuuper high rof.