+1 for saving your money, by the non-window version. It is like getting a free PMag every time you buy 3 non-window versions....
(You'll save money and it will keep you from having to start threads where folks are gonna flame you for thinking a bit farther out there than they do.....)
Seriously, how often in practice (or battle) are you gonna need to look down and see "how many rounds are left".....
Personally, my process is shoot until I hear a click when I'm expecting a "bang", I summarily drop the mag, then insert a fresh (read "heavy") mag into the well, then release the bolt, good to go again..... Here's the cool part: ALL the mags on the ground are empty, the mags in my pouch/on my belt are fully charged....pretty simple "round indicator" system and it costs you nothing extra!