I would also like to know what the advantages are. I have been using the free version of PDA net and it works well for me. It seams the only limitation is that I cannot use it to access websites that use SSH. A fair trade off for a free app!
There are so many hotspot options for jailbroken iPhones. I use TetherMe and have used MyWi and PDAnet in the past. They all work and I'll use whatever is available first after the 4.3 update.
i paid for PDAnet way back so I guess I have the paid version now too, man o man does my internet run super fast, sometimes i think faster then my cable when i run off of my PDAnet