My best guess:
If you left both balls in their stock cover condition, the ENG is matte or dull and around 1000 grit, while the BB is roughly 1500 grit, and highly polished. As a ball park guess, the BB will handle much less oil than the ENG. If you are on medium to medium heavy oil and the ENG is reacting fine, the BB may skid 50 feet, playing the same line, and never get to the pocket. If you want the BB to replace the ENG rather than complement it, then you will have to sand the BB to around 800 to 1000 grit.
If the BB is not replacing the ENG, then leave them as they are and when the heads are too dry for the ENG or the lanes are just hooking too much, the BB may be a good go-to ball to complement the ENG. ENG: medium to medium-heavy oil and the BB: Medium to medium-light oil. Just a suggestion.
I'd think the drilling is closer to stacked leverage than label leverage; that's a fairly strong drilling for a Blueberry, but may work fine for you.
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