The reason to take the lump sum instead of the annuity is a smart decision if you can invest wisely. The theory goes, you can take the lump sum and invest it and, with interest, make much more than the annuity.
The annuity is "cash basis", they pay you the sum of the annuity over a long time period without interest. Most mutual funds could provide a much better return than the lump sum.
However, with the stock markets over the last 4 years, nothing is guaranteed.
I would take the lump sum, myself.