I absolutely agree that in real life you'd have to look down slightly if you needed to check your supplies.
Neither system is going to fully recreate reality, though, so it's just a case of gauging which is closer to the reality of the battlefield.
I'd posit, though, that looking at the bottom corner of your screen and seeing your ammo count, whilst still seeing the scenery of the place you're fighting in is probably more realistic than looking down at a fisherprice toy to see your ammo count, whilst seeing the scenery of a flat in Tottenham and a cat curled up in the lap of a dole-waller sat there in his onesie.*
*I'll concede it slightly depends on whether the locals are rioting, though.