Best barrel length for SBR, 10.5, 11.5, 12.5..?

[Pappabear]

I think you need to back up a step and ask yourself a few basic questions, and once you've answered those questions your length issue will probably resolve itself.

1. Why do yo want an SBR? Home defense, no car, train in desert
2. What is the maximum distance at which you require you ammunition to perform as desired? Not far , any ammo, not LEO
3. How Flexible is your ammunition selection (i.e. are you restricted to department or agency issued ammunition?)? My choice
4. Do you intend to add a suppressor? Oh Yes at some point
5. If so, do you know which suppressor you'll be adding? Oh No
6. If so, is it a QD suppressor with a mount and what mount is it? Will be QD, what mount ???
7. etc. This is going to be expensive

I started my study a while back. I'm trying to learn more. I just put a Brakeout on one of my 16's, but for the Brakeout, not the can. I like the idea of Surefire cans with minimal POI shift. What is the average length a can adds? 4/6 inches?