Mid-Length is the best compromise in my opinion. Even with a 16" barrel you get a longer sight radius and a slightly better gas system. I really see no advantage to the carbines with the short handguards.
I've had rifle versions, but rarely used them.
I agree. I like the old 20" pencil barrel but really today's 16" midlength offers a lot. I now have three and no 20" nor 16" carbine gas.