I'm interested, too, and found these specs:
http://www.kia.com/us/en/vehicle/sorento/2016/features
Q. for those who know- why the torque difference? V6s list 252@5300 and regulars 260 at 1450 rpm? Tow specs are the same (except for AWD which goes up for the V6).
The difference is between a non-turbocharged 3.3 L engine (252 lb-ft @ 5,300 rpm) and a turbocharged 2.0 L engine (maximum torque 260 lb-ft @ 1,450 rpm). I wouldn't call the turbo the "regular" engine; the base equipment is a non-turbocharged 2.4 L engine (178 lb-ft @ 4,000 rpm). Any engine is optimized to work best (which means getting air and fuel into it) in a limited range of speeds, but the turbocharger pumps air into the engine over a wide range of speed, and the net result is that typical modern turbocharged engines (which includes all diesels) can produce its maximum torque at a relatively low speed. In this case, the peak torque is at 1,450 rpm for the turbo, versus 4,000 rpm and 5,300 rpm for the two non-turbo engines.
The ability to produce good torque at moderate speeds is desirable for engines that need to work relatively hard continuously, such as when towing. This is the only reason (other than fuel consumption) that diesels are desirable... and it is the turbocharger that gives diesels this low-speed ability, too. This might be a reason to prefer the turbo 4-cylinder over the larger non-turbo V6, even though the larger V6 engine has a higher maximum power output.
Keep in mind that while this low-speed torque is a desirable characteristic, any engine still needs to run at relatively high speed to produce its maximum power (such as to climb a mountain grade at highway speed):
2.4 L non-turbo: 185 hp @ 6,000 rpm
3.3 L non-turbo: 290 hp @ 6,400 rpm
2.0 L turbo: 240 hp @ 6,000 rpm
Down at 1,450 rpm, the 2.0 L turbo with the accelerator pedal to the floor will only be producing 71 horsepower; it has to spin faster to do more work. You're probably not going to be doing much towing at engine speeds this low.
Rated towing capacity usually has much more to do with durability than power; the fact that it goes up with AWD suggests that Kia is concerned about drive traction, control, or axle durability, not just the engine. The fact that it goes up with AWD for the 3.3L non-turbo V6 and not the 2.0 L turbo 4 suggests that they are concerned that under sustained high load (such as climbing a mountain), the turbo engine will not be able to avoid overheating with a heavier trailer; turbochargers cause cooling challenges.
