The Suunto Ambit range is designed to give you the ability to record your performance through a variety of activities. The latest incarnation is the Ambit 3 which comes in various models, all of which feature GPS, compatibility with a Heart Rate Belt and Bluetooth connectivity.
The Peak is the top of the range model and has the most features and the longest battery life.
The Vertical has most of the features found on the Peak except the weather alarms and extended battery life. It does have a smaller body than the others.
The Run is specifically for runners. It has all the functions for running but doesn't have the multisport or outdoor functions. It does have a thinner body than the others.