My F250 with camper package uses the same springs and running gear as the SRW F350. The only difference was the wheel package I selected and a 2" shorter axle block.
As posted, the advantage of buying a F250 over a F350:
1. Lower rear allowing garage or fifth wheel clearance
2. Lower insurance and registration fees due to lower GVWR
3. Lower price
The initial lower rear will make it squat 2" lower when loaded. If you plan to load so much that the headlights are shining upward, you better off starting with the F350 unless the advantages I posted are a priority.
I would not hesitate suggesting the F250 for any bumper pull trailer unless you also plan to carry a heavy load in the bed (sxs or golf cart). For these types of loads, you would have a better chance of less sag and no need for suspension aids by buying a F350.