flats on active basses sound great... You will typically have more inherent mid-punch and less treble to worry about overall, which can pleasingly alter the sound of some super modern active basses.
I had la bellas strung on my active. I liked it, but from what I read here a lot of people prefer it on passives. I don't really know how to word it, but it sounded more powerful on my active bass when compared to my passive.
