I am by no means anywhere CLOSE to an expert. But I would say you need the heavier springs. The preload and springs depend on your weight as much as your riding style. If you want super-plush riding for cruising around trails, the softer springs will give you that feel while still being able to handle your weight. The stiffer springs will handle your weight when racing in enduros or cross-country. Also would probably work fine for some MX riding!
I put something like .41kg springs in my bike as I weigh about 185 on the scales - so pushing 200 with gear ready to race. I race in enduros occasionally so I wanted to be a little on the stiff side for the setup.
I followed Race Techs recommendation and the similar advice from a local cross-country racer that does suspension work and have been happy with the setup.
I hope this helped some...
Good luck!