Porsche cayenne V6 or cayenne S ? is there a big difference?

You can compare the models side by side on the Porsche USA website: http://www.porsche.com/all/comparemodels/Compare.aspx?pool=usa&language=none&model1=92AAG1_249&model2=92AAH1_249&model3=&compTab=0 My quick comparison suggested there are a few differences between the two, but none really that significant except for the engine. I would also expect maintenance to be a bit more for the Cayenne S (for example, it'll need 8 spark plugs, not 6...) but neither should be astronomical to maintain, if driven properly and serviced on schedule. If you consider 0-60 in less than 7.5 seconds, and a top speed on "only" 142 MPH to be "bad" performance, then go for the Cayenne S for $13,000 more (plus extra fuel and insurance cost). Personally I would not pay the extra cash for a Cayenne S; there's just no need for the extra engine for an SUV that one would not race or take out for a track day. Now, for a 911/Cayman/Boxster, I would consider the "S" versions since they are performance vehicles from the ground up.

The V6 is a little sluggish, if you are an aggressive driver and demand power you must go with the Cayenne S because the V8 is a more suitable engine for this SUV.

Yes! The most significant difference is the engine. The V6 is a Volkswagen engine. Yeah. That's right. The same engine that you'd find in a Volkswagen CC sedan. Personally I think that's a joke, and that Porsche should hide their hideousness from the world for a few years and try to earn back some respect, but that's another story. Besides that small detail, the V8 also offers about +100HP, +200HP for the turbo V8. Repairs are going to be costly for both. If that's a concern, this is probably not the right car for you.