The break fill on the Korg is a great idea (same on the Yamaha's), but it has one significant problem...
If you only have three fills per style, and one of them is a B/F, that's leaves two regular fills for the entire style... simply not enough for a four variation arranger. It is, I believe, one of the contributing factors to the overall lack of smoothness in Korg fills compared to Yamaha and Roland.
It is WAY past time for Korg to change to a six or more fill system... Others manage it with little drama, and variation to variation fills would work smoothly no matter WHAT direction you went in.
A four variation arranger needs twelve fills to have one for each possible transition (not counting fill-to-same). Yamaha have six, Roland have seven, but if you have a B/Fill, Korg have TWO...
Not good enough, IMO.
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An arranger is just a tool. What matters is what you build with it..!