that's highly subjective thing (people and basses seem to like certain things in strings).
they are not overly expensive if you're into experimentation.
I can tell you what I like:
Sadowsky black label flats for a 5 string P/J. That's what I have on my L2500 and P5.
I sort of wondered what my Devon 5 might sound like with flats, I will keep the black labels in mind if I decide to go that direction. I know what you mean about certain strings being complimentry to certain basses, what works great for one may pale on another.