Quoted at bottom is one of my initial comments on the game, from the "Nerding out on slots" thread. I assumed the Mega would be important because it pays 3x on the free spins, whereas the Mini only pays 1x. But I stalked a slot AP and discovered he was more interested in the Mini.
Later, Mickey posted the frequencies (on Twitter). The Mega bonus requires ~1830 spins to trigger. Mini is ~221.
So although the Mega pays bigger, the long wait interval mitigates the value.
It's a tricky design. I assume Mickey watched or played the game and noticed the "Mini" symbol appearing much more frequently on reel 5 than the "Mega." It must be a very long reel strip. I've tried analyzing YouTube videos for some games, but videos are usually only posted because something interesting happened, so you'll find mostly bonus rounds. On Harleys, bonus rounds use a different reel set.
Then he studied the Harley Davidson meters, but didn't choose the 88/30/25 on the left. Instead he played the right machine with a 37 at the bottom. Top and middle were approximately 15 and 25.
He presumably valued the mini more significantly than the mega or maxi. (Although maybe he was saving the big mega for last. 
) He played rapidly, stopping the reels instantly each spin.
I looked in again about 20 minutes later, and he had moved to the left machine, but was again targeting a bet level with a high mini. The highest mini I had seen was 35 (at the 400-bet!), but it's (unlikely but) possible another player had built it higher in the interim. I observed him advance the mini from 54 to 56. Then I looked again about 45 minutes later, and he was still playing with the mini at 94!
