Since your kills will be mostly long distance, you won't be running over ammo packs like you would be if you were running around the map. Once you run out of grenade rounds, just OMA and re-pick your tube class and you replenish. With Scavenger you have to physically run to the downed enemy to get the ammo off his dead body.

It sucks in the beginning since 6 seconds can be an eternity and you are hella vulnerable but with claymores you can lock up a spot pretty easily since most people dont even look for them. Just level it up to OMA Pro and it makes it a pretty viable option and arguably the better choice over scavenger.