Internet purchases

I am going with credit card payments because when I have had issues in the past (with sellers/merchants), they pretty much stood behind me. I have only once asked Paypal for the same support and it was like pulling teeth. I believe that (like credit cards) you have to know what their parameters are for backing you up. If it falls outside their guidelines, they will let you know right away that "their is nothing that they can do".

As far as checks go, not very many people or businesses want to deal with them any longer (unless you are talking about cashiers checks - which would be a different story).