I think the "dual" rating description is very helpful when meeting up with strangers to set accurate expectations.
When someone describes himself as a "strong 4.0", it is often someone who doesn't play USTA leagues, and is actually a very weak 4.0 at best but doesn't realize that he is innocently mistaken in his self rating. This over-self-rating situation can lead to embarassment if the meetup results in a mismatch, and these over-self-raters are so abundant in the non-USTA world that the NTRP rating scale practically get redefined outside of league play. I often describe myself as a 4.5/5.0 to set accurate expectations and not get lumped together with the over-self-rated guys. In other words, the dual rating (4.5/5.0) description is way more legit than "strong 4.5."
There is also a second reason that the dual rating helps in my case when setting up meetups in other cities:
I live in a section that seems to have systematically depressed NTRP computer ratings, for reasons that are not entirely clear. That is, a 4.5 computer rating in Seattle is not the same as a 4.5 rating in most parts of the country. I'd estimate maybe 0.2 difference, based on my experiences traveling around (hence my username) and competing against other computer-rated players around the country. I believe this NTRP level offset is reflected in PNW's disproportionately high rate of success at nationals.
