I am afraid that is a investment related question and is best directed to your investment advisor.
From a tax point of view, however, I personally don't think it is an efficient retirement strategy as an annuity is already a product that accumulates earnings tax free! So, really, one would not generally purchase this product in a retirement account.
I have spoken to a few financial advisor's and have found out that many of them do not favor putting retirement funds into an annuity. According to them, it doesn't make sense as these accumulated earnings are already growing tax deferred. Again, the decision is entirely sure alone, but, then why not put these funds in a long term CD at your bank! This would be the safest option available without incurring deferred sales charges that are imposed on an annuity!
Remember, the Annuity is not a cheap product to purchase, it is a fairly complicated product and if understand the costs,purchase the right kind of annuity with all the guarantees and additional features, and are willing to allow the annuity to accumulate earnings for a period of at least 7 years, then you would possibly enjoy a higher rate of return due to potential bonuses that you may receive. With the financial strength of the insurance companies, you may very well get the security and protection that you wish with an annuity!
But, like I said, I strongly suggest that you discuss your particular situation with your financial professional.