The Emerald, as a pearl, is going to have less of a range of utility across oil patterns thana solid will. You can scuff up a pearl to a certain degree as Curly learned, but you usually do not want to scuff a pearl too far. That will cause it to grab the lane too early.
A solid's cover can be modified more easily to handle a wider range of oil (in my opinion, which may or may not be worth anything these days).
I have to believe that discontinuing the Blueberry, having been Lane#1 most generic ball, that is, it covered the widest range of oil patterns and bowlers' styles, was a major mistake on Lane#1's part. They have large range of balls, but each one of their currently available balls covers too small a range of conditions.
PROPOSAL:
Since they've had the pink raspberry, the black raspberry, the blueberry and the cranberry, maybe the need to resurrect the PK18 or the newer Brunswick Activator coverstock as a solid resin over the C2 core and call it the Blackberry.
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"Just because you can do something does not mean you should do it."