Should I buy the mylar bags for sketches

Hey guys. So far, whenever I have a douga or genga I just put it in a polypropelene cel bag but, now that I am getting more into some CG sketch only series and my sketch count is rising . . . I was wondering if I should buy the mylar bags or if the poly bags are about just as well. What do you think? The reason I've hesitated is I'm afraid if I have two kinds of bags I'll get them mixed up and I know i don't want to be putting my cels in mylar bags. That's a no no.
Anyone else already face this decision?

hello I use mylar exclusively here is a rundown from my dealer about the differences...

http://www.egerber.com/aboutpreservation.htm

Another thing is that mylar is absolutly crystal clear unlike poly. It really looks better too.

Where can you find mylar bags that are large enough to fit cels?

I bought a bunch from Noriko's anime. They are large enough to handle the large cels and even the regular cels too. ^_^

http://www.darkharbor.com/trades/html/celbooks.html

IMO her prices are quite reasonable and yes the bags do seal. However the bags aren't fitted like the ones Rick or Curt uses so there is space for the cel to move. Not sure if that is an issue for you, but figured you should know. Cheers! ^_^