Which is better? Amazon or ebay? also with their customer service cause so far, with ebay, it sucks. Haven't tried with Amazon. And which one is widely used by people for online shopping? But most of all, which one is really better as a seller?

For customer service Amazon is much better. They are all for the buyer. Ebay is cheaper...sometimes. I prefer Amazon for the speed of shipping and I know that if I buy from the marketplace (third party sellers on Amazon) that Amazon is 100% on my side.

The sense I get is that Amazon has a good selection of new items, but eBay is cheaper if you're willing to buy used items.

I've never used the customer service of either site, but I've never needed to either.

Which is better? Apple or housebrick? Walmart or Boeing 747? Eiffel Tower or an armadillo? Go on, answer the question, which is better?

THEY ARE DIFFERENT. So neither is better. Your question is meaningless.

Both are good as long as you seek out the best deal.