I am 15 years old
Having been in the Marine Corps, I took from your username that you were too. A Gunny (Gunnery Sergeant) is arguably the most revered rank in the Marine Corps; a name like "iGunny40" will look to many people on this forum like you're representing yourself as being a Gunny. I'm sure it wasn't your intent to misrepresent yourself and I'm also sure you meant no disrespect from it, but this is just a heads up; Marines hold the rank of Gunny in very high regard and I'm sure this won't be the last time someone mistakes you for one based on your username.
As for the DI vs gas piston debate, I'm mostly a DI guy myself. In my opinion, the drawbacks of a gas piston design are only worth it if you don't like cleaning very much, if you mostly run suppressed (though short-stroke piston designs tend to be louder with a suppressor than long-stoke piston or DI designs), if you're in 12-hour firefights, or you're using your weapon as a light machine gun. I prefer the accuracy, simplicity, parts interchangeability, and lower weight of a DI design. Even when I was in the Marine Corps infantry I didn't see the DI design as a drawback; it takes no time at all to pop the bolt out, quickly wipe everything down, CLP it up, and throw it back together.