It depends upon prevailing interest rates.
The amount you get from lump sum is based on the amount of money the lottery would have to invest in US government securities with a guaranteed payment that would mature on the annual payment dates of the multiple year payout. That is effectively the net present value of the future payment stream at the prevailing interest rate.
If the prevailing interest rate is low (like now), take the lump sum as you would get the highest present value. If prevailing interest rates were high (e.g., like in 1980), then take the payments so that you invest some of the money at better rates later (rather than taking the hit up front for the high prevailing rates (lower present value)). Currrent and future tax rates also impact your decision, but who knows what can happen with future tax rates (other than going up?).
Third issue to consider is: if you take payments and die before the full amount is collected, can the uncollected payments be willed to your heirs? If not (and in many states it is NOT), take that into consideration.
Remembering that the lottery is ENTERTAINMENT ONLY (one of the worst "investments" ever), I think that in most cases you should take lump sum.