I'm not sure if there are any functional differences between this and the regular model dune racer but the regular model is apparently the best one in regards to going off road (grass) out of the box. The dune racer model also has the most seat room for larger kids.

- Powerful like Batman! Monster Traction system drives on hard surfaces, wet grass, and rough terrain
- Goes 2.5 and 5 mph (4 and 8 km/h) max. forward; 2.5 mph (4 km/h) max. reverse
- Holy details! Awesome Batman graphics and Bat Wing front fenders, too
- Shhh! Secret storage compartment for crime-fighting gadgets, toys and more
- Sturdy steel frame and metal side bars

http://www.amazon.com/Power-Wheel...PDKIKX0DER