Yea I was in the same boat. I couldn’t decide. Here’s why I chose the 11":
True, the extra length is relatively negligible, but shorter is always better for my needs and I carried both before deciding which one was the keeper. The 14" comes with a head shield. I took this off to slim it up a bit. As you will notice, this is useless unless you are running drills or shooting lots of rounds. If you are running drills then it’s a nice touch as it keeps the barrel from burning you (and it weights basically nothing as it’s aluminum). The LPA rear sight on the 14" is quick-detach and mounted on that picatinny rail. Great if you are planning on running a red-dot or similar sight, but not so great otherwise. I found with my gun (and my friend’s exact same 14" models) that the rear LPA sight mounted on the rail causes the POI to be significantly high. Even when bottoming out the rear sight and raising the front post all the way up, it still didn’t quite fix the problem. Mind you this was at close ranges (out to 60’ or so), and before anybody argues this point, my 870P w/ Scattergun Tech ghost rings was bang-on in the same situation.
The 11" has the same LPA rear sight as the 14" only it’s mounted directly to the receiver. This is great cause it lowers the POI. And overall the 11" is just a smaller tighter package, and after throwing on the SGA stock, albeit heavy, it really tightened things up.
Here’s the specs on both:
14" Fabarm w/ factory stock (12.5" LOP) = 32.75" (832 mm) OAL
11" Fabarm w/ factory stock (14" LOP) = 31" (787 mm) OAL
11" Fabarm w/ SGA stock (13" LOP) & S&J sling plate = 30.1" (765 mm) OAL
Hope that helps.