Out of the box is a meaningless measure. If you haven't cleaned it yet you can develop a variety of misleading opinions.
Both have usable triggers but each unit will be different.
For me the question is not which is best out of the box but which is easiest to obtain an excellent trigger for.
Answer is M&P. Install the Apex Tactical Sear and Safety Plunger and you will have an excellent trigger that XD's can't match.