Core may be more experienced and skilled.

However, they are trying to change Bitcoin into something I don't want it to be (a settlement network).  Not only that,
they do not listen to anybody but themselves (and their corporate Blockstream investors and controllers).

BU team might have more buggy code by your metrics, but they are coding what I want -- a Bitcoin by the people, of the people, for the people,
that is in line with Satoshi's vision, in line with free market dynamics, and lets Bitcoin scale organically on the main chain.

This is what is driving the popularity of it.