The estate tax break, which will cost $68 billion in lost tax revenue, has little economic impact because it mostly affects the already affluent, who are less likely to spend their tax savings.
Those savings could be in the form of investments which will help drive the economy or as deposits which become incremental capital for the banks to lend. Unless the "affluent" stuff all of their savings in the mattress. Even then, I'd rather have it stuffed in a mattress than given to Congress to spend on such economic "stimulus" as African junk washing.