Completely agree with all the positive eBay comments. Use Pirateship for shipping. Totally integrated with eBay (pulls in orders and updates eBay with tracking numbers once you buy the label). Get cheap/lightweight poly mailers from Amazon. And use this handy chart from Pirateship to know how much for shipping. Weigh everything before you post it. I started with free shipping on everything and find that my things move faster when I charge accurately for shipping. I honestly think it's a mental math thing. lol. $17.99 + $3.99 shipping seems cheaper than $22.

I was using Mercari for a few months last year and it wasn't worth my 30 seconds of copy and paste time. My sales last year were 50% eBay, 50% PM. Take the commission % into account, if all of those were PM, I would have lost $400 in just commission.

Set it and forget it is completely accurate! Until you sell something on one platform, then make sure you deactivate it from the other platform. I can't tell you how many times I've had interest on the same item within 24 hours. Crazy!