From some quick research a lot of people say they are not as good because the paper ones trap the smaller pieces of dirt and what not, but then many people like them.
Here is what one guy says
"It's not so much that the dirt gets trapped in there, it's more the fact that it can't filter the smaller particles a papery type can. The micron rating on a paper type filter will be much higher than a stainless, because there is a limit to the size of the holes that can be drilled or punched into the mesh sides of the stainless filter.
I am not so sure about this, for example RO filters I have are a stainless membrane, and I am not talking the cheep one they sell at home depot,
I am talking on a molecular level smaller then anything I am worried about in my motor! sub micron!"