The entire process of getting a SBR is a logistical nightmare. I hate the stupid governments rules, and waiting 8 months or more for a stamp. That's why I only have one SBR. That being the case, going with one that's only a little bit shorter like a 13.7 or 14.5 makes zero sense in my book. (unless you're gonna pin & weld the flash suppressor to make it legal without the stamp) If you are going to the trouble of getting the stamp for the small package, get the small package. I went 10.5".
You only have to SBR one lower, and then you can use it with multiple uppers of different lengths and calibers.