I know many that has had Ford diesels...6.0 and 7.3's. The ones that have owned both prefer to have the 7.3's, suppose to the more durable of the 2. I personally crammed 30+ pounds to an 06' F-250 4x4 4 door with 5" exhaust, cold air intake and a controller with no issues what so ever. As far as how hard to work on them...I couldnt tell you I had 100,000 mile warranty that I never had to use and traded it in.
1/2 of 03' the finished using the 7.3's and switched to the 6.0.