Currently gathering parts for a PDW build. I am considering two barrels for this build. The 11.5" Faxon Gunner and the BA 11.5" Modern Series. I was contemplating 10.5" but I understand that the 11.5" would be more reliable than 10.5". The main difference I see between these two 11.5" barrels is the gas system. Faxon is midlength and BA is carbine. Should this be a serious consideration? I don't plan on using a suppressor but you never know what the future may hold. I would likely use an adjustable gas block, but I wondering if either of these barrels would be more reliable than the other due to the gas system?

11.5" pencil barrel.  Bonus points awarded for a pinned Ti low profile gas block, i.e. V7

I don't believe either offer an 11.5" pencil barrel.

BA makes a 11.3 Hanson profile with a pinned gas block that is similar to a pencil profile.

I have no experience with the Faxon 11.5 Gunner but it seems like it would be finicky with ammo because of the gas system.  I have a BA 11.5 standard barrel and have put all kinds of ammo through it with no issues.  I have quite a few barrels from both manufactures and they both make great barrels and I've never had issues with either.

Right. I have a couple of Faxon barrels and both have been great. Never owned a ballistic advantage barrel. Until now. Ordered the Modern Series 11.5" from Tom's Tactical for $99 shipped. Seemed like a great deal. I looked at the 11.3" Hanson but the differences between the two weren't enough to sway me toward it for the price difference.

BA lightweight 11.3" with pinned gas block

If you get a BA, get one of the performance series that already includes the pinned gas block.

I have some of both and the nicer ones are much, much nicer.