If you look at and follow financial advice, one then should consider a pension, no matter how small or large, as part of your balanced portfolio, In other words, consider how much you would have to buy in bonds to get an interest yield equal to the amount you receive in pension. An example is that if you assume you can get an interest rate of 2%, then a pension of $30,000 a year would be worth %1,500,000. If you have $1,500,000 in your 401 savings plan, then in effect you have a 50/50 balance portfolio with 50% of your money in "bonds" and 50% in stock. You can change this balancing as you see fit.
Based on the above, I see no reason why a person would choose a lump sum and have a risk of finding a decent yield on the lump sum you get.
A retired IBMer
Ken