For a working gun, synthetic is better, but only if it's rigid. Many of the synthetic stocks on factory rifles can be accurately described as "Tupperware." They don't have to get damp for an impact change, they are bad all the time. Laminated wood feels "warm" like walnut, but it's heavy. Really stiff synthetic stocks aren't cheap, so are seldom seen on rifles on your dealer's display racks. Walnut can be made water resistant by applying wax to the stock's interior, under the barrel and action.
Your choice, but I like the warmer feel of a walnut stock against my face.