On a $40 jacket
On Poshmark, the fee is $8.00, so you keep $32.00 and the buyer pays $6.49 for shipping. On eBay with $8 shipping, the total sale is $48, the fees come to $6.93, and you pay about $8 for the label, so you keep about $33.07 after shipping, before packaging. eBay leaves you a little more, but Poshmark is simpler. The calculator above does this for your own figures.
Which is less work?
Poshmark. You don’t have to work out shipping: the label arrives by email. On eBay you choose the service, weigh the parcel and set the price.
Which has more buyers?
eBay, by a long way. Poshmark’s buyers are fashion shoppers, which suits clothes well but not much else. For everyday non-fashion items, also compare Mercari.