The difference in power between the 5.2 and the 5.9 is 25 HP and 30 ft/lb torque. Both engines are thirsty and anemic by todays standards, but I don't think you will feel much if any difference if you were able to find the bigger van with the bigger motor.
For the record, I had a 1994 Dakota with the 5.2 (as well as some Grand Cherokees) as well as a 1996 Ram 1500 with the 5.9, and used them to tow a 4500ish pound boat. Couldn't really tell a difference between the two engines from what I remember.
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010