It's a Navara that lets you smell the manure you're hauling. Simple as that.
Okay, there are a couple of other technical differences, but they're all related to the tail end of the car - up front they're pretty much the same thing. The Pathfinder is shorter, with coil suspension on the rear, so airbags can be added without worry of causing damage to the chassis.
The distance between the rear axle and the towball is much less, so the effect of a heavy trailer on the car is reduced. The longer that distance, the longer the lever, and the more effect a heavy tow ball weight has in lifting the front wheels of the car (so the Navara will need a WDH more than a Pathfinder). Yes, I tow a 2.5T van and yes, I use a suitable WDH (Weight Distribution Hitch). I prefer my front wheels to be firmly on the ground, so that I maintain the vehicle's balance, braking and steering control - that's what a WDH is for. The Pathfinder won't be as sensitive to a heavy load - but if you have a van that's "up there" in weight, then you should still consider it. The chassis of the Pathfinder doesn't have a problem with the WDH as long as there are enough mounting points of the tow hitch to the car.
The Pathfinder also pitches more when off-road and has a slightly better turning circle. This is because the Navara's rear axle is further back - the Pathfinder is about 300mm shorter in wheelbase and overall length. For towing it'll make the Navara marginally (and almost unnoticeably) better. For off-road use it'll be an even race - the occupants of the pathfinder will be thrown about a little more but the Navara doesn't have as good a ramp-over clearance - that extra 300mm in the Nav is significant.