Hi John
My Sorento is a Mar 2004 model the latest ones have a 5 speed auto box on them. I have only ever used the sport mode to knock it down a cog when overtaking in a hurry or when on a steady gradient when the auto box changes down and then back up again. I press the sport mode button and it will hold in 3rd gear until we get to the crest of the hill, then I knock it off and it goes back into top gear.Hope this helps.
P.S my van is a 1600Kg MTPLM. the car handles it very well and the auto box is superb.
Regards Jim