If you get a good magazine shingle, you won't get anything in the magazine. I rocked magazine shingles for my M4 in Afghanistan, and I never had a problem of getting nasty gunk and shit in my magazines, and the dirt there is like moon dust. I find it best to use both, personally. Something similar to Raiths kit. Its good to have magazines that you can get IMMEDIATE access to, and to use the pouches with flaps to replenish your shingles. The difference to some people may also be how you load the magazines into the pouches. If you have your rounds and the top, you would want something with flaps, if you load them rounds down, shingles will work just fine. IMO, a good magazine shingle won't have retention problems. I use Battlelab shorty magazine shingles, and they have something to grip them on the inside, as well as a tight retention cord(which also has the grip stuff on it). I love em, and the work great. Coyote Tactical has my preference for mag pouches with flaps.