I love my can as well. I am just trying to determine the most reliable length. I have fondled the Daniel Defense MK18 and like it. I played with Harsh's 12 and like that one too. Being tall and lanky figures in the equation. What about a port selector?
I have a 10.3" DD MK18. Love it, obnoxiously loud though. My suggestion for a first sbr is get a factory gun of whatever brand you prefer. It's a long wait for the stamp and only getting longer. You want that gun to be reliable from day one and not have to tinker with the set up. If I couldn't have gotten my DD MK18, then I'd have gone for a Colt 6933. BCM and Noveske also make an excellent factory gun.
I have found a MK18. How badly does it corrode the flash hider? I saw an AAC brakeout that was corroded badly after 3K rounds. I am not waiting 2 years to get a Larue OBR. I do like the idea of a factory gun, though. Noise will be handled by a can.
I haven't had the opportunity to put enough rounds downrange and find out. I'm also still running the A2 flash hider. I think with that short of barrel, you're gonna see erosion sooner rather than later. The real issue is when you start trapping the heat and gasses in a can. Most people I know of run some sort of brake to prolong the like of the can.