I can tell you why I would buy it, and that is the connectivity (which can make use of its overload abilities), the design (I like the fact that it's properly heat-sinked, unlike the XP-520) and the superior efficiency at high output levels (less heat generated + proper heat sinks = cooler operating regime), however I wouldn't pay more than ~125$ for either of them.
Don't get this wrong, I like the XP-520, but I wouldn't put it in an case with no airflow (fanless system or sorts), the Silent Night gives me that option though.