I prefer the Pyrex for packing and warming leftovers, and apparently the cost difference is not that great (the 8-cup Gladware is more in this instance). I find that the Gladware (or any plastic-ware for that matter) gets lost much more easily, and requires replacing from loss if not from wear. Moreover, the blue lid and glass of the Pyrex containers are definitely more forgiving when it comes to forgotten leftovers.

Pyrex 18-piece storage set; $29.99 or $1.66 per piece.

versus Gladware:

Gladware 1-3/4 cup (6 pack of 5 piece); $19.32 or $0.64 each

Gladware 8 cup (3 count), $5.99 or $2.00 each