Two different M4s that I'm looking at. Matrix/AIM ($80-$100) - Full metal - magpul stock, magpul RIS covers, and a new mag puch. - "The whole inside of the gun has been re done. 350-400 fps. Purchased about 9 to 11 months ago" - "To be honest I have no Idea what's in it I putt to much to remember and I got it in a airsoft store not online so I can't giv a link" Cyma ($145) - Full metal - "The only part that I changed was an upgrade using the m115 piston spring. All other upgrades were done using its standard parts to bring out its potantial and longivity. Five hours were spent on this piece. First the gearbox and innards are completely taken out and thoroughly cleaned. The bushings are CA'd in place. The piston receives a new o-ring and its head is tightened securely and CA'd so it doesn't come loose. The cylinder OD & ID is polished. The cylinder/cylinder head/air nozzle is completely sealed for excellent compression when checked manually with piston. The gears were meticulously shimmed and spinned freely with gearbox tightened. All components were properly greased and installed in the clean gearbox shell. Motor height was properly adjusted. The hop-up assembly was taken apart, cleaned, reassembled and then sealed. Test fired for smoothness and chronoing." Opinions? If they were equal price I would definitely go with the Cyma, but the other one is so much cheaper that I am also drawn to that.