Yes exactly, less strategic. If you can pick between the 2 weapons at all times, you don't have to put thought into their pros and cons. If you don't have money buy the a1-s, if you have buy the m4a4 (unless you'd rather have a a1-s, then just buy it). If you have to drop, just drop the right weapon. There is no decision to be had but the normal economic decisions you already had to take, while if they are mutually exclusice you have to weight their pros and cons, not only for you but for your team.
Plus, there being people that use the a1-s while they are mutually exclusive forces everybody to somewhat know the weapon, raising the skill ceilling.