There are no pro's to a 5.4. That price for the 6.2 with 50k miles @ $34k is good assuming everything else is in great shape. You said it was a one owner truck too, so I'm guessing it's in great condition. I would jump on that one. Once you start looking at Gen1s with over 75k miles, you need to factor in the price for new or rebuilt shocks along with a number of other needed maintenance services.