The best I can put it is that the Rockabilly Blacks and the Silver Slaps are fairly close tonally (they use most of the same material), but as Francois pointed out, the main difference lies in the final nylon covering.
The Rockabilly Black uses a black nylon material that we flatten in-house, and then polish smooth. The Silver Slaps (Golden Slaps, Super Silvers and Psycho Slaps) all use a clear round nylon that is then sanded down smooth. Same final process for both, except more material is removed from the latter. And, because the clear vinyl is originally round, there is a bit more flexibility in those strings.
What that means for the tone (understanding that all instruments are different and have their inherent character) is the strings using the clear nylon tape are a bit more "alive" in the pizz, whereas the flat nylon tends to dull the attack. Easiest analogy I can give is like comparing a J and P Bass; one has a more forward, throaty attack and the other has a big fundamental punch.
That said, the Silver Slaps are still smooth to the touch. I'm currently using a Super Silver/Silver Slaps hybrid set (I like the more stout E/A strings) on my Corvann Baby Bass and there's no texture to the strings.
Hello all - I recently decided to purchase and try a set of the Innovation Rockabilly Blacks, but I'm having trouble finding them in stock. Has the Rockabilly Black line been discontinued? Many thanks for any help you can provide!