The higher the weight rating, the happier you'll be towing. That truck is most likely too heavy (w/ trailer) for most 1/2 tons, save some of the newest ones probably.
Sure, you can tow it with the half ton, but she won't like it if you do it on a regular basis.
If you get a 6.0, get it tuned for 91/93 octane. Well worth the money from all the research i did and everyone i know that has done it.