^^ isn't that just the PLM cover?
The main thing when searching for a diff cover is to decided if you want it for looks or function. If you want to go offroading, then a solid one is needed (not aluminum) but if you are racing, then a finned aluminum one would work.
Then you have to consider price. Some are cheap and easy while others are a bit expensive but have the most bang for your buck.
Personally I would suggest the MagTec cover since its holds the most fluid and looks nice in my opinion. It also has a fill gauge and a temp gauge option.