MSM SI owner here - wishing I had went with the blue. I had picked MSM to blend in more with traffic (and cause of those ugly fake rear vents match better with MSM) but now I kinda got bored with the color.
I got the MSM and love it, but we also have a MSM Accord. The MSM does allow everything to blend in on the car, so the accent's definitely don't stand out as much on the MSM. In my area, it is definitely hard to find any MSM sedan's at dealers. I like the rarity of the color compared to the rest.
I originally wanted white but none could be found around me. There was a MSM nearby so I went with it based on the same reasons others have stated. I'm in my 30's with kids and am not a fan of the ridiculous bumper vents. The idea of the vents, and car as a whole, blending in really appealed to me for a DD. I just want good handling, good mpg, and low maintenance. I don't need to be noticed. Also, I don't have time to wash my car every weekend so the fact that the gray hides road grime well is a HUGE plus!
I went MSM out of necessity. I wanted blue or white, but none were available in my area, so I was able to snag probably the last 2018 MSM, taking delivery end of October or first week of November. Honestly, I think MSM is now my favorite color. Installing a type r red emblem is going to set off the red lip I will add, plus the wheels I am adding have small, red accents which will bring the theme all the way to the red emblem out back. It will be subtle, but help it stand out from the crowd some.