I raised a comment on the original question about required minimum distributions (RMD).
I did a little spreadsheet to answer my own question to my own satisfaction about RMD. There is a function-of-age component of calculated RMD after age 70.5, with a lookup table published here:
If the spouses are different ages, and you have a goal to maximize your estate, option 2 or 3 can be valid because of RMD. 8 additional years of tax deferral in the younger spouse's account before RMD can be worth the 1% spread in returns.
One of the known gotchas of RMD (which applies to 401k and trad IRAs but not Roth IRAs) is that it can force you into higher marginal tax brackets year over year by a process that you have no control over in retirement. If stacked on social security or other sources of income, this will reduce the marginal value of your IRA in the future, or cause taxable capital gains or dividends to be taxed at much greater than 10-15%. If you are on the cusp of "upper middle class" this is something to consider; if you are aiming for the middle of middle class, you will probably need more than RMD to live on anyway, and thus this less of a consideration for you. Congress could always change the capital gains rates back or do another wholesale Gramm-Rudman style overhaul, enact Mike Huckabee's FairTax, etc. so compared to other answers, this is both esoteric as well as making decisions for 40 years from now on top of the sandy clay that is US tax policy. That said:
Based on assumption of a 1% spread in returns for each spouse, a split can be sensible for the goal of estate maximization and retirement income bracket gaming with an age spread of around 8 years (so if one spouse is 40, and one is 32, they ought to split; either option 2 or option 3 in the OP). The 8 additional years of tax deferral in the younger spouse's account before RMD are worth the 1% spread in returns.
If the spouses are the same age or spouse A is younger, maximize on spouse A.
I hope the screenshot is self-evident, but I can elaborate. The lines mark hidden years.