I've had the we m4, the we scar, and the kjw m4.
I found the range to exceed the average aeg at 400 fps .30 gram bbs.
But after the hop up spin takes effect on the flight path, the shot consistency goes out the window. The groupings are roughly ten to twenty feet wide after the 150 to 200 foot mark.
I found pre hop up flight was just as accurate as any aeg i've had though. Which is why I'd only use gbbrs for cqb.
Also to consider is the odd flyer and sometimes a shot will land 20 feet in front of you.
All things considered, I get more accuracy, consistency, equal gas consumption and range from a properly tuned double stack gbb pistol. But nothing is more fun than a gbbr on a calm, windless, sunny afternoon