I think gumtree is becoming more popular as ebay try to keep squeezing seller's for every last dollar they can on a sale.

I sold a bunch of surplus container project pins last year on gumtree and they lasted one weekend after selling to multiple buyers. Some of these were to interstate buyers which makes the process a bit more complicated but when you have shipped pins internationally then interstate is a cakewalk. If you are selling a higher priced item on gumtree like a pin then my tip is to ask for a holding deposit after a potential buyer makes contact in the early stages of the negotiation which will identify the genuine buyers from the timewasters.

You've probably noticed on ebay how many have asking prices that end in "250" - that is to cover the chance of a sale through ebay as if someone clicks buy it now the seller is automatically up for a seller's fee of $250 on a higher priced item like a pin, then you have to a add paypal fees as well if they go that route. Gumtree on the other hand has no fees (for a basic listing) so you have more flexibility in terms of both listing price and negotiation on sale price.

I do watch ebay but I wish that seller's would be a bit more careful with the handling of their pins as the number of listings which have to be cancelled after "getting lost or broken" particularly after the item has been listed for a few days is very disconcerting.