I've never owned a W&S, however, I have owned a few Bernies and I enjoy them very much. If you're looking for really light weight in a 12, you could keep your eyes peeled for a Bernardelli Elio. I think mine with an English stock weighs barely over 6 lbs with ejectors. Though, it also has the 25.5" barrel lengths and is choked in IC and Mod. The articulated trigger is also nice if you are carrying a light gun and shoot heavy pheasant loads in it. The bores are also chromed (I'm not sure on the W&S), which makes cleaning a breeze.

If both guns are neck and neck in the running, I'd choose whichever fit you better.