The 3:73 will give slightly better gas mileage, the 4:10 will most likely have a somewhat higher tow rating. When looking at specific vehichles, check the info on the driver side door jamb for towing information. You may have to look up the code in the owners manual.
2012 Toyota Tundra 5.7 Litre DoubleCab
6 speed, 4.30 Limited Slip, Tow Package
2013 Jayco White Hawk 27DSRL
2010 Jayco JayFlight 26BH sold
Yamaha EF2000is Generators (2)
1996 Honda CB750 Nighthawk