From Darwin "Major engine work on the Ford requires removal of the cab. If you have a cab over then the cab can't be removed which means increased labor rates. Pop the hood of the two motors and decide which one you would rather work on if you had to.
Ford used the Bosh Cp4 injection pump, it has a less than stellar reputation. Unfortunately Ram in 2019 went with the CP4 also, these pumps are more sensitive to fuel, less of an issue if you plan on staying north of the border, but in my mind not a pump I would put a lot of faith in. Also, when they go, they require a cab off repair (on the Ford) and over 10K$$ in repairs because the metal shards take out the entire injector and fuel system."
Respectfully, it is a myth that cab removal is mandatory for engine work on Ford 550. Any engine work can be completed without the cab being removed to include full engine swap. However, it can be a lot easier/quicker for your mechanic if he can remove the cab. I wouldn't let that factor carry too much weight if I were comparing the 550 and 5500.
I won't enter the 5500 cummins vs 550 powerstroke reliability debate: both companies make good motors which any owner, given money, inclination and maintenance effort can turn into a long-lasting, top performer (I own both cummins and Ford diesel trucks and like them both). Both will easily carry pretty much any camper box or trailer you can come up with. It's also easy, if expensive, to find 550/5500 parts and maintenance for travel throughout North America. For the third world, I would look for a simpler diesel solution than 6.7 from either company.