I am not a fan of super light front tyres, they tend to bounce you off rocks (lighter tyres have a faster rebound because usually you need higher psi to stop folding and punctures, the same reason why light rear tyres have a lot of bounce). A heavier front tyre is sooooo much more accurate when riding natural.
Rear tyre, I still say Der Kaiser, it's not like they are mega heavy and unless you are competing in the world champs I would be more concerned on making the bike ride well rather than being a weight freak.