the biggest difference on the surface between WAMU and Lehman is the enormous debt levels Lehman has. It could take many years to figure it out and some estimate it at 100b. If it is that high there will be little to nothing left over regardless of a settlement outcome.
WAMU has much less debt and a real case here. They are both risky as there is no certain outcome in either but i would bet much more on Wamu then lehman for sure..