Gumtree is a second hand marketplace platform that enables you to sell your unwanted second hand items. Facebook marketplace, although is born later than Gumtree, is growing rapidly.
Recently (at least for past one year), Gumtree is filled with international scammer targeting expensive items asking you to send the item to another country with a fake PayPal or bank receipt. After you post an item on Gumtree, most of the “buyers” who chat to you are these scammer and they find your email and phone numbers so you would also be overwhelmed by scam emails and SMS.
This is the only reason yet enough for a user to leave Gumtree. Facebook marketplace, compared to Gumtree, is a good second hand platform. It has lots of active users to support it so that its platform can be very active. Once you post your item to Facebook marketplace, there will be lots of real buyers chatting with you, not scammer.