As a married couple, you could open investment accounts separately (one or two) or jointly. This is not about IRA or Roth accounts, but for standard investments, in the US.
For this question, ignore all issues coming out of a potential future separation [so assume 'they lived happily everafter']; what reasons speak for the one or the other?
Are there any ways to save taxes by doing it either way (compared to the respective other way?), or anything getting easier/more complex? What is easier if one of them dies, in either case (it's going to happen one day)?
I have reviewed Unmarried couple, should we open a joint investment account or separate accounts?; that is about a Permanently Unmarried Couple. Situation and recommendations might be different for Married Couples - or not?