I stopped at the 3750@80 PSI Nitto Terra Grappler as I could use the factory forged aluminum rims and 7500 lbs. at the rear axle is good enough. By selling the factory Firestone tires the cost for the upgrade to the Nitto tires cost me in total less than $500. With a 19.5 tire I would have to pay an extra $900 for new rims and find 19.5 rims in a 8x180 bolt pattern and good luck on that.
The 19.5 tires are highway treads and designed for onroad truck use and long tread life. I prefer something that is better suited to dirt roads and sand and snow.