The lump sum is supposed to be the present value of the income stream - or perhaps the amount it would cost to purchase an annuity. So the numbers are roughly equivalent in terms of real value.
The estate tax would be on the present value of the future income stream.
Under IRS regulations, as I recall, nothing happens until the identity of the winner is made known (by his claiming his winnings, I assume). But at that point income recognition is retroactive to the date of the drawing. Stu