ZandraJoi how a paid one would offer more security.
I tend to believe that paid software are equally vulnerable. Because in the end, they are also built using PHP and use almost the same setup at the server level.
But they do offer a lot of in-built features. Plus features that are provided through the community by means of add-ons.
ZandraJoi What stops me tho is all the add-ons & that some you have to pay for to help your forum run smoothly.
If you can skip many decorations, the only charge that will incur is that of the domain name and hosting package. Good luck when you are reay.