I'm glad I didn't order the diesel. I'm in the middle of a Western New York to OBX camping trip using my Father's 78,000 mile 2000 F350 dually diesel supercab and I can tell you I won't miss diesel on bit when my 7.3 gasser arrives. I don't think the diesel gets much if any better fuel economy towing as my last truck got (5.4 3V). It got about 8. The dually, high 9's maybe. I expect the 7.3 gasser to deliver the same-ish.
Don't get me wrong, the dually tows amazing. So stable. The 7.3 diesel doesn't car about my travel trailer being behind it. But it's a noisy, rattling, smelly thing. I'm sure the 6.7 is unbelievable and paired with the 10 speed is amazing, but the break even for that upcharge will never happen under my ownership. Between that and pumping diesel from pumps that somehow are always filthy when I do find them and def....well...that can be a thing for someone else.
If you are a diesel guy more power to ya. Just not for me.