for SHTF work - I have my Vepr with a shitload of polymer 30rd mags.
For target shooting, plinking, and having fun - the AR-15 with 20rd USGI mags are used. I swapped in green followers for the straight mags and they're not as good as the alloy follower namely:
The plastic (black or green) followers lack "tails" at the rear of the follower (the part that hits the mag catch) that prevent it from tilting forward. The alloy followers DO have these tails and you can't tilt them forward.
The Vepr isn't as fun to shoot becuase it's not as accurate, the recoil is stronger, muzzle climb w/o a muzzle brake is a bitch, and its loud and crude. That makes it a great SHTF battle rifle though (engagements under 100yd, great stopping power, ultra reliable - not saying its more/less reliable than a properly maintained AR-15). It's not as fun for me because i have a splitting headache and sore shoulder after about 120 well placed shots. I can burn through 2000 rd at the bench with an AR15 without so much as a headache (but a big adrenaline rush)