Something to keep in mind is that with a shopping cart you'll need a way to process credit card payments (MIVA may offer that.) but with paypal a customer needs a paypal account to make a purchase.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.