Otis, my man! Remember Animal House?
The primary differences between the two models is that the:
Police Magnum will accept extended mag tube.
Police Magnum has the Parkerized finish.
Police Magnum has sight upgrades available.
There is a wealth of information available comparing the merits of these models on TFL. Rather than conducting a search, you could even read all the posts going back a few months to get a complete picture.
Good luck with your choice, I've learned that one of the side benefits of getting the extended magazine tube is that the gun flexes less and feeds a bit more reliably.
~ Blue Jays ~