Yes, the treasury will give you 3% a year and if held for 30 years you get your principal back. The annuity will give you 5% a year for your life, but you have lost your principal.
in realty the immediate annuity gives you back your own money at a higher cash flow rate then you can take it from yourself .
an immediate annuity has no interest rate . it only has an implied fictitious rate of return the irs uses from a life expectancy chart for tax purposes .
so you give the annuity company 100k and they give you 6k a year . 16 years later you have all your own money back
now you go on their dime and get your first dollar of return .
so lets look at a portfolio of 200k consisting of 100k in an annuity and 100k in stock vs 100k in bonds and cash and 100k in stock .
trying to match that 6k cash flow from the annuity from bonds and cash will deplete them to zero and require refilling from equity's .
the 6k annuity will never end reducing the need to sell as much in equity's .
unless your own investing has the most favorable sequences odds are the annuity /equity's will give you more cash flow and depending on how long you or a spouse live more for heirs.
the annuity has no sequence risk which allows you to spend all of it keeping no powder dry for poor sequences .
on our own we have to keep a lot of powder dry because poor sequences can leave us with near zero left at the end of 30 years to more than 2x what we started with .
that money can't be spent up front since we don't know our final outcomes .
the annuity has no sequence risk like our portfolio's do so they provide a higher cash flow ..