Don't look at to early of a 7.3L, back in the early 90's they where not turbocharged.
I would pick the V10 if you are just using it to pull the trailer, and not putting more than 5,000 miles a year on the truck.
The oil changes are much more reasonable, and the truck overall is much lighter. Unless you are planning on finding a dually. The crewcab F-250 4X4 only had a 865 pound weight rating with the 7.3L engine in it! GVWR was only 8,800 pounds while the curb weight is nearly 8,000 pounds! The F-350 has only marginally more capacity, at 9,900 GVWR until MY 2004. In 2005, the GVWR of a SRW F-350 went up to 11,000 pounds for the gas engine and 11,500 pounds for the un-desirable 6L diesel engines.
So if you are looking for the V10, check out MY 2001 and later, with 2005 being the 'heavy duty' version with a LOT higher cargo rating. The F-250 in 2005 and later has a 10,000 GVWR, while 2004 and earlier is only 8,800 pounds. Gas engine is about 700 pounds less than the diesel.
GOod luck!
Fred.