I have a 2003 Sedona DX (US Version)
The Sedona will probably have you riding a little more upright, and have a little more adjustability due to the adjustable stem.
The differences are basically that the Sedona is oriented to riding on paved roads and smooth paths with an occasional relatively easy trip off road. The Rock is oriented toward riding off road. You would find the Sedona would ride a little more efficiently on the smooth surfaces, but would not perform as well in the rough stuff.
Another option, if you are really oriented toward the road/smooth path, to take it even one more step, is the Cypress, which is basically the same as the Sedona with smoother tires in the 700c size. Slightly less capable for off road, but slightly more efficient on the smooth path.