I read the 19 pages of this thread till the end post at this moment, and I have changed my mind at least 10 times as to when to take SS, and at the end I can say for sure I am confused, I will start my spreadsheet now and check what if scenarios. I will be 62 this coming December.
That happens a lot, it is a complex subject.
Your plan to "what if" things is smart. Here are some things to think about:
1) It is
impossible to "optimize" the "when to start SS" decision unless you
know when you will die, what the future changes to legislation will bring, and how the market will perform. However, it may be possible to optimize the
expected outcomes of various courses of action by making assumptions about longevity, taxes, market performance, SS changes, etc. Obviously, the results will depend a lot on those assumptions.
2) When doing your "what if" scenarios, in my opinion it makes a lot of sense for most people visiting this site to concentrate on the situation where your investments do poorly (e.g. a decade or more of essentially "flat" equity performance, bond returns that lag inflation, etc). Why? Because if your investments at the start or retirement will be "enough" to support necessary/desired spending given
normal historical returns (which we test with FIRECalc), then the big unknown is you'll still be okay in the case of a black swan series that is worse than the historical data set. If a person's investments climb to the moon, then when you take SS won't have any practical importance. If your investments plummet, then the decision on when to take SS may prove to be really important.
I'm planning to defer SS to age 70 (though I'm still mulling things over . . .). Maximizing the size of that inflation-adjusted lifetime monthly SS check provides a good backup in case Mr Market decides to take a long slumber. I'm not concerned about whether this provides the highest expected returns because 1) the assumptions needed to make that calculation are too uncertain and 2) I'm more concerned with avoiding a very bad outcome than in doing all I can to get the highest monthly total income.
Good luck!