While I have a Bruiser I used in its stock polished state and I have 2 world Class particles balls, I haven't sanded a Brusier BUT I have a Nemesis on which I made the surface finer, from 800 grit to 1200 grit. SO I think my comments should be valid.
I think the stock World Class will fit above your 1000 grit Bruiser, BUT I think it may be 1 1/2 to 2 steps above it. The World Class is in Lanemasters class of their strongest, oil loving, oil needing balls: WC, Big Bang, Terminator (not polished), AP2 and the Yeah Baby!
If you like the WC, and many people do, then to make it fit closer to a single step above the sanded Bruiser, I believe you should probably sand it to a finer grit, like 1500 or 2000 grit.
One of the very good things about these balls is their covers are easily adjustable with sandpaper or abralon or Scotch Brite pads. In fact, I believe that Lanemasters/Legends particles respond best to sanding, rather than polish.
If I were you (and you'd probably do this anyway, but I feel I should say it), before I sanded any new ball, I'd try it in stock form and then adjust it with sanding, as needed OR desired. Just make sure you try the base ball several times to insure that house blended oil patterns are not disguising differences. I've seen that happen too many times to count.
FYI and as an aside, I compared my Masterpiece to my Brusier and found the MP earlier and bigger hooking than the Brusier, with similar, but not exact drillings and stock surfaces. On my lesser oil pattern, I needed the Bruiser's better length and energy retention (but that's solely because the house didn't use enough oil for the MP to be useful.)
Good Luck.
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"None are so blind as those who will not see."