For sale is an almost new FN 10.5 inch barrel. Bought it, built a gun, and then a Daniel Defense MK 18 pistol became available, and don't need two 10.5" guns, so replaced barrel with an 11.5". Pre dimpled for a Geissele Super Block gas block, but could easily be re-dimpled if needed. Somewhere...
What he said. Also, it's nice to not worry if a direct thread will loosen during firing. On the flip side, you may lose a slight amount of precision, but not enough to worry unless you're shooting really long distances.