"Urushi", I believe, refers to the art of lacquer application.
I recently saw a chart comparing the various versions of the Urushi. It seems to agree with what you say. Only the Vermillion is somewhat distinctive. I would buy the Blue, because I like blue. In terms of output, the Urushi is a "tweener". I am not sure it has quite enough output to drive just any MM phono stage, but it does not need much more gain than what is typical for such a stage. It seems popular to bash the Koetsu line these days, but the Urushi still gives me great pleasure, and I now own several other cartridges with which to make comparisons.
I recently saw a chart comparing the various versions of the Urushi. It seems to agree with what you say. Only the Vermillion is somewhat distinctive. I would buy the Blue, because I like blue. In terms of output, the Urushi is a "tweener". I am not sure it has quite enough output to drive just any MM phono stage, but it does not need much more gain than what is typical for such a stage. It seems popular to bash the Koetsu line these days, but the Urushi still gives me great pleasure, and I now own several other cartridges with which to make comparisons.