Pathfinder vs 4Runner for towing

I'll be towing a 6x10 cargo trailer around the US quite a bit - the trailer weighs approximately 1k, the gvwr is 3k and I probably have approximately 1k of merchandise or so inside. I'm looking for a reliable mid size SUV to tow it with, and have landed on a Pathfinder or 4Runner from the last 10 years, maximum price $15k?(not interested in American Chevy's, Fords, Jeeps, Dodges, etc - I've had my share). I was hoping to go with a RWD V6 to keep gas mileage down as it will also be my only vehicle, but also don't want it to be underpowered. Any thoughts on which would make a better tow vehicle, or anything else I should consider? Also, should it definitely have the tow package? I'm not sure if the tow packages ad a tranny cooler and/or if I can add get one installed if not.

Background info - I towed the trailer with a Dodge Sprinter last year. Love the Sprinter, but it didn't really like towing across all of those subtle inclines of middle America, and definitely not steeper inclines, and it was a borrowed vehicle so time to get my own.