I'm a diesel mechanic and trust me go with the 7.3. I've had mine for 5 years and the only problem that i had was the tranny and the cam sensor, the tranny problem was due to the power that it is making and towing. i got a turbonetics ball buster turbo, 120hp chip, exhaust, cold air intake, 8" lift w/ 38" tires on 20" rims. i did upgrade the tranny though, tripple disc billet converter, redline clutches, transgo tugger valve body kit. oh yeah, and there a hell of alot easier to work on. If you do get one and your going to tow with it, i highly recommend getting a good converter from BD, or ATS. hope this helps.
I would suggest a TC as well as a valve body. PM Lord Tauk, he has a TC and vb on his 7.3.