This issue has been beat to death here, so often that at one point anyone posting additional diesel verses gas threads had them deleted.
Never the less, it's always a good subject for discussion, more so for new folks. My personal opinion is based on owning both a 5.4 and a 7.3 in the last year. I could have kept either one, but I chose to sell the diesel due to a number of factors including the much higher cost of maintenance for the diesel, (a simple oil and filter change can cost north of $100 verses about $30). The list of potential diesel expenses / upgrades is pretty long and expensive verses the gas motors, which seem to run for hundred's of thousands of miles with nearly zero issues. It's also far more likely you can find a mechanic willing / able to work on a gas motor much more often than diesel. Having said that, plenty of folks enjoy their diesels in far away places with a minimum of issues, but for me, the simplicity and economy of maintenance, less noise, and lower cost (diesels bring a premium price when sold) won out. I probably spend a little more at the gas pump, but for me, gas is a minor expense. As for a 6.0, I'm happy for those folks who find them reliable, but they have a long history of very expensive failures so I would never consider one. Best of luck in your search. When you find the right one, be ready to fly if needed, and do it immediately or risk loosing it to someone who can move quicker.