Ah; like "left Twix vs right Twix," eh? (In case you're unfamiliar with the reference: 'Twix' is a candy-bar which is two identical 'candy-rods' sold in one package, and a popular series of commercials has started a "myth" that the two rods are made in different factories with slightly different methods.)
I guess it depends on what you buy. Ebay is a bit unorthodox for shops, but I've bought from plenty of successful businesses on there. I mostly use Amazon though because of the more integrated review system, though, as I like to know exactly what I get for my money.
Both but according to the needs,The thing is when we talk about Electronics then Amazon and for general stuff Ebay is good too but the thing is people have become choosy because of Scam ratio on Ebay which is a little over the top now a days but there are some trusted vendors there so they can be considered.
You just can't beat Amazon when it comes to customer service. Every time I have the smallest complaint or concern they will either ship me an entirely new product (sometimes not asking me to ship one back) or give me a large refund to compensate + I get to keep the item in question. Also, most online money making programs like InstaGC, Swagbucks and alike, they all provide Amazon gift cards. eBay on the other hand, while you can get some steal of a deal from time to time sometimes that can be meant in the literal sense. The stolen or fake product market on there is huge and while Paypal disputes tend to always favor the buyer, they can't do much if say 3 months down the road it turns out your phone was stolen and no longer works. All that in mind, never had a problem with Amazon. Always feel like I'm gambling with eBay.