Of all the pages out there, PVC-Free pages are probably the safest...but...since the cards are usually PVC, cheaper pages with PVC 'might' not hurt them (but better safe than sorry).

However, the PVC pages (which are usually Polyester or a variant) CAN react with PVC under the right conditions - only time will tell the long-term consequences.

Now, when talking about "surface printed" cards, or cards with player photos, etc. - MORE issues will come up (plastic reacting with the dyes, etc.).

I truly believe there will NOT be a 'one-size-fits-all' answer for storage (much in the same manner that some chips bleed on flips when stored). It may be that 80% of cards will store one way, 10% another, 9% another, and the rare 1% will have to be handled with kid's gloves.