Unfortunately, I don't think I can answer the best body type question until I get to see the pro's and con's of each. I don't believe that all the body types were open to play at Euro-gamer. (can't say for sure due to not being there) Allow me to use a MAG reference (sorry, I hear some of you moaning), originally the light armors had speed, mobility and increased load-out room while the heavy armor lacked that but made up for it in damage protection.. Several updates later there is no difference in speed or mobility it's now just about how much equipment you have room for.
While I have much higher expectations for Brink, I will still have to wait until I get to try out each body type before I jump on the "HULK SMASH" Heavy bandwagon or the "Knuckle Draggers Drool, Lights Rule" bullet train..
The good news Spring is now one day closer..
Weapons are based on bodytype, so there are Heavy, Medium, Light, and Sidearm weapons. Each bodytype is able to carry one weapon from their bodytype and one lesser weapon. So a Light player is stuck with a light weapon and a sidearm, a heavy can use a heavy weapon and a medium weapon.
SMART movement and speed are also based on bodytype, lights are able to move the fastest and get the highest, being able to reach ledges 15 feet (5m) up, medium players can climb anything at eye level, and heavy players are restricted to waist height, and move the slowest.
The final difference between the body types is health and skill points (these are used up by skills and slowly regenerate), lights have less of both, heavys have more.