Well, my gut was to go with the 10.5 inch barrel, it looks like you guys all more or less agree. Thanks for the input!
My other idea for another build was to get a 13.7 inch barrel and get a long flash hider pinned and welded getting the barrel length over 16 inches. I guess that is the shortest barrel possible to do that with. I always thought it was the 14.5 inch barrel. I currently only have one AR, but I think I need 5 total.
1. My current 16 inch go-to gun, the jack of all trades
2. My half finished 10.5 inch pistol build for vehicle or close quarters work. (I might transition that to my main go-to gun if it turns out nice)
3. A 13.7 inch pinned/welded non SBR build
4. An 18 inch DMR/SPR type gun with an A2 stock
5. Another 16 inch beater truck gun.
And maybe a 300 Blackout pistol upper just because... America!
Now to convince my wife...