Here’s my 2 cents as to why, all aluminum construction, weathering option, more detailed bridge as well as diferent bridge options. The construction is such that you only need to make a round hole, and use the adjustable tabs for mounting. This is a more compact option than the Ross.
the Ross wood construction is bigger, deeper that the Millhouse. Ross makes many nice things, and at one point it was a top option, but since millhouse came out, I believe it surpassed the Ross.