There is no right and no wrong answer. In some cases the lump sum will be significantly less valuable actuarially because it is usually the value of the age 65 benefit and may ignore subsidies available at early retirement. But then again, most of the plan that offer windows provide only a QPSA as a death benefit, so that there is a significant forfeiture at death (a total forfeiture for the unmarried)...the lump may be knocked down by the potential for forfeiture, but theres no chance you get zero.
At the end of the day, normally the lump sum and the annuity have the same value using conservative assumptions. I believe most will take the lump sum
because they are guaranteed to get "something" and that something is usually a LOT of money
they dont want to end up with "nothing"
they have concerns about the security of their pensions long term, if Detroit doesnt have to pay...
they have concerns about the extent of the PBGC guarantee
AT the end of the day, the lump sum is better if things go bad (short life, money crisis etc) and the annuity is better if things go good (long life, no crises etc)
People arent worried about what happens when things go good