I would get the 4.30's. The 10-speed trans will give you decent mileage when not towing, but there's no substitute for that mechanical advantage of lower gearing to get the load moving when you are towing. The 4.30 gears will make it easier for the trans to do its job and will likely help it last longer before it needs a rebuild. The 4.30s will really help when you need it most, like backing into a site...
FWIW, a good axle shop can re-gear a 4x4 for about $2k. Might be worth finding a used one with the 3.73s, then if you don't like how it tows, have it re-geared to 4.30s. I wouldn't sell everything to buy a new truck just to get 4.30s.