The blue moon seems to have the tendency to "fuzz" up more than the tachyon. That is neither a good or bad thing, just an unscientific observation.
Both ropes are really excellent products though, I climb with both and would say that both are real solid performers.
I would advise against fast decents without a pulley or friction saver. All my Blue Moon and Tachyon ropes have clear glazing where in the sections where I have run it way to fast over tree bark. Not the ropes fault......totally mine.
If you are a new splicer, and want to splice your own rope, the Blue Moon will probably be an easier one for you to splice, but other than that you can't go wrong.