I mainly drop ship. But if I have to choose I would go for Amazon. Also have a look at Walmart and AliExpress.

Good luck, Cheers!

Ebay tends to pay a little better but the problem is the listings are transitional, meaning you have to constantly update them after the bidding stops. You can choose eBay stores and this will help with this situation, but your still at the mercy of the store owner. Also, I was making some decent income with eBay affiliate a few years back, and then the changed the rules making it much more difficult to earn. I have since heard they have relaxed those rules recently, but once there's bad blood...
Another alternative is Walmart. They have a fair amount of products that you could use to sell.
Best Regards,
Jim