Found an error in the spreadsheet with some interesting results. The tightness in play required to benefit from any given rake structure is directly tied to the rakeback number. (I had determined this earlier, but wound up not posting the message.) Also, the point at which one rake structure becomes more profitable than another it always when it costs you zero to play.
In English: If you get 30% rakeback, you need to be contributing slightly more than 1 - 30% less rake than the average player to benefit from higher rake, at which point you'll be paying a net of zero. So if you get 30% rakeback and can somehow manage to pay ~73% less rake than the average player at your table, you'll benefit from a higher rake structure. Otherwise, always take the lower rake.
Maybe this will help explain it:
Now to add bonus into the formula...