One of the many, many, cool things about Alembics is that the electronics allow so much flexibility that there is no one string for slap.
One of my Alembics almost always wears DR Black Beauties. I like the feel, tone, and durability of the coated roundwounds. I get all the zing I want (or need) out of those. I also use the same strings on two Music Man Sabres. Again, all the zing I need.
My other Alembic wears Ken Smith Burners or Rock Masters. Mainly because I bought a whole crapload of them years a go for practically nothing and I am slowly working my through them. They are not bad, I just like DR BB and DR Phat Beams a LOT more, so those are the strings that go on my gigging basses.