RPS AllStars, Marbalizers, Premium. In that order.
Distance. Barrel length.
Time to install.
When directly compared to my "14 Lapco Bigshot and "12 Dye Utralight on my A-5 the Flatline got much farther distance with a flatter trajectory. I don't have enought property to tell how far it shoots. I can shoot trees at the back of the yard from ~120' with good consistancy.
It takes a little time to install or remove but becomes easier with use. Of course I rarely remove it from my marker. With it I'm able to shoot players who's shots don't make it to me with any force. It's smaller size is nice for crawling through the woods or ducking behind a bunker.
If you own an A-5 this is the best barrel to get. Just make sure to get good small paint.