This is kind of funny topic because I just quit my 9-5 to start a business creating software to let people sell on many marketplaces (including eBay and Etsy). Basic idea is you put in your product info one time, and then sell on many markets at once.
For personal history - I did very well over the years selling MtG (Magic the Gathering) cards on eBay . I could run searches on things like misspelled card names I knew were common, and win auctions for 50% or so of the price. Then turn around and resell this item back to eBay with the correct spelling.
Have not done a lot on Etsy, though my wife loves it.
Few tips that I see our best sellers do on both for artisan type goods.
1) Brand it as YOU. There may be 10000 people selling purses. But only 1 YOU selling YOUR purses. Make it clearly yours, and explain all the extra work you put into it.
2) You can sell at a premium price, but you have to be reasonable. Not many people want to spend $300 on a purse. (But maybe that is your niche, in which case go for it, but have reasonable expectations). Free or discounted shipping on multiple items is awesome, as it can help encourage people to buy more.
3) Fill out all the search terms. Etsy has 13 I believe. eBay has no search term box, thus your eBay title ends up being very important.
4) Good pictures. More the better.
Depending on your market, Amazon is also not a bad place to sell things. Things you can eat tend to do really well there. It costs ~$50 a month sell there though, so you need to be doing a decent volume to justify it.
