I have spent a ton of time on both sites. There are 2 advantages on ebay that I would love to see resolved on jackpot:

A larger selection of chips from all over. Jackpot seems to be primarily Nevada.

A link to paypal that makes paying very easy (not as important to me as the first point).

If this changes I would be just as happy, if not happier to spend my money on jackpot. I prefer to support club members.