Other aspect to consider is cost of replacing DA over Ultegra with cassettes costing more than twice as much.
I don’t know that this is really a consideration. I tend to replace the consumable parts with the compatible Ultegra pieces. It is just a lot more affordable that way. When you buy an initial groupset it is often cost effective to just get a whole kit in one trim level, but a lot of people who own DA use Ultegra cassettes and chains. You can even use 105 someday when 11 speed makes its way down to it, but I personally draw the line at Ultegra.