The 4-banger is a reliable little engine, and while it may leave you wanting a bit more power on the highway, it will stand toe to toe with the 6 cyl on the trails if geared propperly. I personally have a '94 with 130,000 miles on it, and with some mods (ignition, injectors, air filters, gears, electric fan, high-flow cat, cat back system, etc.), it happily rolls down the street on 33" tires at 70 mph. The torque curve starts a bit below 2,500 RPMS, and pulls all the way to around 4,000RPM's pretty strongly.
Like bounty said, if you regear it properly, so that you stay at around 3,000 RPM's, you could drive all day without issues.