Another gripe on the 7.3l ford, they want over $2k extra for the 7.3. That is 20% of the way to a diesel and you know that powerstroke will be worth $8k more at resale.
Part of that $2000 is the 10 speed on the F250. On an F350 the 10 speed is included on both the 6.2L and 7.3L so the cost is less. If it were me, I would buy the F350 and then de-spring it to soften the ride. That way I get the GVWR for when I need it.
As awesome as a diesel is, I don't want to own one unless I have to. I don't drive enough for the fuel difference to offset anything.