On the topic of the CA M15 - good gun all around. Probably the best overall gun you can get for its price. But you will more than likely have to upgrade or repair a few (reasonably cheap) piston-related internal compoments sooner than you would another gun. IMO, not a big deal at all. The gears are solid, the wiring is top quality, and the mechbox shell is built like a brick shithouse compared to other stock V2 mechboxes in guns of that price range.
I've seen, held and shot the TM boys M4 and bigger piece of crap I have yet to see/hold/shoot
The word "BOYS" in the name sort of gives it away, now doesn't it? lol If you're looking for an AEG for gaming purposes, then someone would be a retard to get any gun listed as a Boys model for that purpose. They have low velocity (TM MP5 shoots about 150 FPS, Palco M4 shoots 135) and plastic gearboxes. And they're only designed to shoot .12g BBs.
However, for a kid 12 or under wanting to shoot, it's a fantastic little gun. The TM shoots nice and straight and consistently (10 shots thru my chrony, and ALL between 158 and 163 fps), has an adjustable hopup, and can spew forth BBs at a rate of 12 rounds per second. For a kid, that's an awesome little gun for learning to shoot and for plinking. My son was extatic that I got him an MP5 "just like mine", since my MP5 is his favorite gun. And honestly, in terms of cosmetics, his MP5 looks better than my JG! So yeah, for kids, they're awesome. For an adult, look elsewhere.
And I should say that the Firepower Boys M4 is not a bad little gun for the $63 price tag either. I painted the receiver flat black and the furniture OD, since my son wanted it to look just like my C8. He really enjoys shooting it.