I'm going with 62. For me, it absolutely means pulling the money from the 403b if I don't take Social Security. The time value of money must be included in the calculations.
A while back I ran a whole bunch of scenarios to try to understand what the choices would mean. It appeared to me (and I think that I am seeing some of this in everyone's responses) that "it depends". (Really helpful, I know.)
For my personal situation, using some round numbers because I can't find the spreadsheets right now there were basically three situations:
1) IF I retired with a net worth less than about $500K, I would HAVE to take SS at 62 just to make ends meet.
2) If my net worth at retirement was greater than, say, $2,000,000, then it was much better to take it at 70 because barring an asteroid, there were there was very little risk of running out of funds and this would maximize my standard of living.
3) BUT, for the range in between, it boiled down to "it depends". It depends on the sequence of returns most importantly. In this range, especially the lower end, NOT having the SS income would cause my stash to become seriously depleted if there were a bad run of years starting off. SS would keep enough of my stash intact to make things viable to the end. If I had a good run of returns at the beginning but was taking SS, then I would end up accepting a slightly lower standard of living in the long run.
This becomes further complicated when adding in different spousal benefit amounts, the inherent uncertainty in predicting life span, differing ages of spouses, etc., etc.
I think that it is just something that requires one to take a deep breath and a long, hard look at the particulars of YOUR situation and make a choice that you can live with. For me, I
think that I will delay until 70 but realize that a couple years of badmarket performance may accelerate the choice. Perhaps one of us will collect early and the other wait. But at 55 right now, I am not going to spend
too much time obsessing over it. I'll revisit it in detail when I turn 61 and 3/4 or so.