The usual benefit of porcelain is that it's on top of metal, and the metal takes a magnet. So if you're going to be putting something on the board that would benefit greatly from magnets, like, say, a timeline that you update everyday by moving a series of magnetic pointers, then porcelain is for you.

OTOH, if you're just going to write and erase as is most typical, melamine is nice because when somebody inevitably comes and writes in permanent marker on the board, you don't feel bad throwing it away for a new one.

We have a mixture of both in our office and I prefer the melamine ones because they seem to have less problems with marker hanging around after being erased. We also have some cheap melamine boards and some nicer ones; I'd recommend spending the money to get nicer ones because the cheap ones also have problems with ink lingering.

However, like the parent said, if you have a use case that requires magnets, porcelain is the way to go.

If you draw over the permanent marker with normal whiteboard marker, they usually both wipe off...

Have you considered glass? My favorite whiteboard was recycled from a 7-foot tempered glass tabletop.