Porter Cable Polisher....

Hey Iv been told the Porter Cable 7424 is one of the best polishers you can buy. Now I have a question its a Random Orbital Sander/Polisher, so would any other Porter Cable "random orbit" sander work if i put a polishing pad on it? Or do you think I should just get the 7424 (I can probaly save $100 if I get a non 7424). Like ones like this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42286&item=4301278096&rd=1

For example or other brands like Dewalt, Makita etc.

Also whats the diffrence between the 7424 and the 7336, they both look identical and are both random orbit sanders...

Thanks!