What are the advantages to choosing a life annuity as a pension payout option over rolling over the money to an IRA and withdrawing monthly from the principal the same amount as the annuity pays?

The question you have to ask yourself is where is the money going to come from if the IRA principal balance goes to zero. If you purchase an income rider on a variable annuity you can secure growth and income guarantees on the benefit base from which you will be drawing your future income.