I have both, and prefer windowed. It is nice to see how much you have. I've beat mine around plenty, and drop them on the ground all the time doing reloads, and have never had a problem with the windows popping out. I think one window may have a little crack in it, that's all.
That said, I like the idea of a totally clear mag better. I am planning on getting some of the clear grey Lancers.
I have wondered myself why they dont come out with clear mags. It would be just as strong as the colored ones. The colored ones hide molding flaws better though so maybe that's why.
To answer the OP I have non-windowed and they run great. I see no reason to go windowed.
Ok, I don't need no stinkin window.
I got my M&P 15 MOE and 4 additional PMags without windows.
I can practice mag changes even when it's not empty and see how heavy it is when I pull it. Maybe I will learn to count the rounds left by feel.
Thanks everyone for the advice.
Is this a great forum or what?
I think this is pretty simple. No window.
There is absolutely not reason to count how many rounds of ammo you have in your magazine. If you think you are low and going into situation in which you need more ammo, then its time to dump that mag and put a new one in.