I personally didn't like the Medela bags as well b/c I couldn't get them to freeze flat. I use the Gerber storage bags. They recently changed them, and I don't like the newer model as well as the old, but still better than any of the others I've tried.
We use Playtex drop-ins, and these bags fit right in the bottles so I don't have to buy separate liners.
Several of my friends use Medela bags and love them, so I think you have to just experiment. I wish there was a way you could just send off for a free sample of all this stuff, ya know?