A decade ago most of my online purchases were from Ebay. Now, I buy from Amazon almost exclusively. There are several reasons for that but Amazon's customer service tops the list. I was recently reminded of the value of their good service when I was looking to buy a sling backpack. I had found a few on Amazon, then Ebay sent me a $5 certificate. I decided to see what they had to offer. I found one I liked on Ebay and went ahead and purchased it...

A few days later I received a cheap looking sling that had a big, weird logo on it...

It came from Amazon and included a note that said it was an Amazon gift. I remember thinking that "Free" was about what it was worth...

But, I received a message that same day telling me the sling I had ordered from Ebay had also been delivered. I had only received the one sling from Amazon, so I was confused.
One week, multiple emails to seller home-garden-and-beyond1 (unanswered for days at a time), even a call to Ebay customer service, and I am still in the dark. It is only a guess but my purchase from Ebay may have been fulfilled by Amazon and that seller sent me the wrong bag???
In the meantime, I went back and bought a sling from Amazon...

Two thoughts motivated that decision. 1) My time is more valuable than to keep fooling with inefficient Ebay processes. 2) If I have any problem with my Amazon order, same as always, it can and will be resolved in a few minutes with a simple phone call.
I do want to add that for a completely hassle-free experience, I've learned over the years to purchase only products with Prime Shipping. My Prime membership pays for itself in so many ways though that, that is not an issue.
What about you? Do you prefer Ebay or Amazon or have other thoughts on the subject?