Hey welcome to the .org, and thanks for your service.
As for engines. I LOVE my 7.3 but it takes more money to make it compete with the rest. I have been looking at the 6.4s new programers and live in a state that it doesnt matter about emissions and diesels, I could be intrested in a 6.4? as for 7.3s they are older and strong, which is why you see alot with high milliage, i have 245K, I think a 6.0 will see those numbers when they become alittle older. To me they are all good engines and have there plus and minus, but I will always keep my 7.3, just hopefully I will pick up a 6.4 or the new 6.7 one day.