I agree that if both countries require you to use their own passport, you don't have a lot of choice, and need to show both and hope for the best.
I've never had a serious problem, but I've had a number of experiences over the years where airline check in staff seem hesitant and uncertain as to how to handle a complex situation. My takeaway has been to try to keep it as simple as possible for the airlines. If I can show the airline one passport rather than two, that is my personal preference.
I'm not predicting dire immediate consequences for anyone showing two passports. But, as others have said, sometimes things are a matter of personal preference. And given the choice, my personal preference is strongly to use one passport rather than two.