I have used both, no problems with either one, but I would recommend Amazon.ca (for Canadians). Anything that I have ordered is generally delivered (Canada Post) within 24-48hrs. NO surprises. no extras for shipping, brokerage fees, customs etc.
With EBay, it depends on where it is coming from, and how it is being shipped (USPS postal, UPS, FedEx etc) I have had to pay extra fees, brokerage, customs and taxes, before getting the package, This is after I paid the seller for shipping.
And time, 2 days to 4 weeks from overseas. In these cases the prices were worth the wait over buying local.
Ken