In terms of the gunplay
According to a new video for Fallout 4, Bethesda sought out some help from its fellow ZeniMax-owned id during the development process. Apparently this iteration is stepping up the gunplay, so id Software was able to help out in that respect. The the developers looked to id for advice from day one, “starting from scratch” with the combat system.
While Fallout 4 and New Vegas‘combat mechanics were sufficient enough, I’m hopeful of this new shift.