By the very design and basic nature of these two balls, BW (Black Widow) and HS (Horizon Solid), their basic ball reactions for the average rev and average ball speed bowler and with average drillings are diametrically opposed.
The Black Widow is more for medium oil than for medium-heavy and goes long for a solid (due to its very fine finish: 4000 grit). The HS is more for medium-heavy oil than medium, grabs the lanes sooner and will have more of an arc, mostly due to its 800 grit finish. Both covers are medium strong solid resins.
The BW also has a mass bias core of medium low strength (apporx .015, I believe).
As such the HS will be better for carrydown and needs slightly more head oil.
If there's no carrydown, the BW will have more backend.
Both balls' coverstocks are easily modified up and down and can be polished or left dull.
Both balls have very good carry power.
--------------------
"None are so blind as those who will not see."