Amazon and eBay are two completely different companies with the same ground purpose, letting people selling their items on to new potential owners.
eBay main area is the auctions, allowing people to list items in hope to get the best possible price.
eBay will charge fees for any listing you will make, regardless if the listing will sell or not.
eBay does though also offer an option called "Buy it Now" which is a fixed price listing, but they still charge you a listing fee.
When you sell on Amazon you choose the fixed price you wish to sell your item for and you do not even need to pay a fee before your item has sold.
When you have listed your item on Amazon you can just sit back and relax until a person chooses to buy your item, the buyer will pay Amazon which will hold your payment until the buyer have verified that the buyer have received the item they paid for.
Once verified Amazon will add the money to your account, and ever body will be happy.
This means that Amazon have added an extra protect for the buyers without compromising on the sellers terms.
When you sell on Amazon you will likely also experience that the average price for most items are higher compared to eBay.
This can have several explanations such as; Amazon buyers are willing to pay more on the same items opposed to the typical eBay buyer is looking to get a good deal on the auction.
The selling competition on eBay is a lot stronger compared to Amazon.
com which also explains the difference in the average pricing.
Another benefit you get when you choose to sell on Amazon is that all sellers are equal in the result search no matter the amount of feedback, positive or negative, the seller has.
eBay seems to give some sellers a disadvantaged depending on their feedback, by making them less visible for potential customers.
This does not mean that all items will sell better on Amazon.
com it simply means that each potential buyer out there are different, and some of these buyers are very loyal towards the site they regularly use.