I use both. I have much better success with Amazon.
eBay just pays pennies now and then. I don't like their methods. They don't pay for clicks. And they don’t pay for sales. They pay for quality leads. It's complex. When someone bids on something, you get a few pennies for it, even if he or she doesn't win the auction. That's because they bid the price higher and eBay made more money. I guess they consider that a quality visitor.
But it still is only pennies. If the quality of the leads is better, you can get more. But I never did well with that and I’m not motivated to use too many eBay capsules.
Amazon pays 4% and up, based on how many sales you send them. I'm in the 6% range. And I get a nice small payment direct from Amazon each month.
There was some talk a year ago about HubPages including Amazon in the HubPages Earnings Program. But that never happened. And I don't see anything mentioned in the Forum about it anymore. It's better that way, leaving Amazon as an external affiliate allows for more control and better reporting of our sales.
The Amazon reports show me that people sometimes buy some other product, not necessarily what I had in the Amazon capsule. They pay commission for anything people order. Nice.