Pros would be easier to maneuver in tight spaces, it will fit in most parking stalls without having the a$$ end hanging over, can bumper tow more than a single rear wheel F350, and higher payload capacity. Cons would be a dually isn't as good as a SRW in snow, mud, slop, etc, can be a pain to tow a gooseneck/fifth wheel with a shortbox, have 6 tires to change instead of 4, and somewhat rougher/bumpier ride from the extra leaves. Don't know who would buy a dually shortbox unless they bumper tow huge loads and throw heavy stuff in the box.
No idea what resale would be. Depends on availability, the economy, mileage, condition, trim level and year. See what other F350 duallies are going for. I think this truck should be priced slightly lower than a longbox because this truck is for a very niche market. Don't see many people with shortbox duallies because they usually haul goosenecks and fifths and there's more room to maneuver a trailer with a longbox. I suppose you could get a sliding hitch though.
I'd get the dealership to run an Oasis report. See what's been done it.