You might find them useful, depending on your strategy and preferences, however. I don't tend to like LMGs or SMGs, the LMGs take too long to reload, and the SMGs do pitiful damage against enemies in the later rounds.
Having 2 ARs means that if you empty a clip and there's still a lot of guys to shoot, you can switch to your off-hand AR and continue firing faster than you could've reloaded. Between rounds you can go back and just buy ammo, or pick up upgrades for these weapons if you prefer them. Remember that you can also carry two primary weapons in Survival - so if enemies are using AK-47's and ammo for that is plentiful on the ground, you can use that gun alongside another AR that you've purchased or found in an earlier round. What is best sniper position on Resistance in Spec Ops: Survival mode? In Resistance in particular, it's pretty easy to set up shop in the center house, like I explained here: When I play survival, I tend to 'live off the land' and take weapons off of dead enemy soldiers instead of buying weapons at the shop.
