The Multi Terrains are designed for rough terrain such as grass and dirt tracks. They are a lot of fun but they can take some getting used to / practise and do give the skater a good workout.  The following videos may give you an idea of what the Multi Terrains are like:

The Quadline Street Skates have traditional 100mm inline wheels and require less effort than the Multi Terrains but still provide a good workout.  They are designed primarily for smooth surfaces such as roads, sidewalks and skate rinks.  Here are some videos showing the Quadline Street Skates:… ? Not in English but gives you a good close up of the skates in actions.