David Banner starts off the stronger and his absorption powers extend to inorganic and 'inert' materials so he should be able to weld Shaw to the spot and then slide a rail into him or something.
Although Shaw can absorb and output far more power than DB (well, DB showed a limit, Shaw didn't), he doesn't start off as stacked and he needs heavy attacks to leech power from.
So, all in all, Shaw can't kill DB but can be killed by DB.