I've used both but only 2 sales on Vinted.
TBH I've been fed up with both sites recently compared to years ago when I sold a lot on ebay with no issues. (I've around 300 positive reviews, all mainly for 'quality' clothes.
My take on it is...
With Ebay it's an auction so better chance to get a good price.
Postage can be 'bespoke' whereas Vinted comes up with the price, there is a default setting for UPS, so you have to say you aren't using it. (They over-priced a parcel I've just posted so the buyer will have a nice surprise.)
The downside of Ebay is that a couple of buyers recently have been very quick to tell me their items didn't arrive and one had the nerve to query it within a few days, even though my 'posting time' was 4 working days and by R Mail 2nd class. She even mentioning raising a claim, and when it did turn up a few days later, she didn't even let me know.
I now have a couple of pairs of good boots that are hardly worn (I ought not to have kept them!) and I want a decent price for them.
My feeling is that Vinted is for fast and cheap sales.
Anyone educate me a bit more? I've heard such bad stuff about Ebay on SM - scammers etc- it's making me wary.