Generally, the payout is based on something around a 6% return providing your monthly payout.
If you're disciplined, invest the lump sum, and withdraw less than 4% when you retire you're better off taking the lump sum. Plus when you die, any remainder goes to your heirs, charity, or wherever you like, versus the coffers of the pension.
Even if you expect to beat the actuarial tables for age, if you invest wisely and can stick to the 4% withdrawal rule you'll die with more than today's principle in the account. Don't think that if you live long and take the pension until you're 100 that you beat the system, you just missed out on even more years of gains you could have had if you took the lump sum 40 years ago.
The only case where I wouldn't advise the lump sum is if you have a spending problem, and need to protect your money from yourself, or if you REALLY need or want the security of the defined benefit and have other non pension assets as well.