Not sure why it's supposed to be either XMR or DASH. They both have a different objective which shapes their development. One wants to achieve privacy and the other wants to push towards mainstream.
I personally put my chips on DASH as all the fundamentals are there and there is consistent growth. One is targeting the less than 1% crowd while the other wants the 99%. Whether this is executed is a whole other question, although I am confident on the development.
But again, I'm sure there are people that have both. I just think DASH will do much better in the long run.
Privacy by default (not optional privacy that you have to "opt in" to use and is not supported automatically by all exchanges and merchants) is for the mainstream, they just don't realize it yet. Make no mistake, Monero is targeting mainstream adoption (today defined as all Bitcoin users and whose definition will expand over time). Privacy matters for everyone, not just the 1%