Quoted from Snailman:
Unfortunately, It's not a big difference in current code. I like the reward vs risk of Mustang Gears MB much better. This feedback has been provided to Stern,and I hope they tweak it.
3-ball jackpot starting value: 500K
6-ball value: 1M.
And sadly the Super Jackpot base value seems fixed regardless of # of balls.
But you have the benefit of more balls bashing the toy box and the AEROSMITH targets while ball save is running.
The downside of doing two 3-ball MB instead of one 6-ball is that the 2nd Toys MB locks are twice as hard to lite locks.
I'm sure that some people would bash Stern for just copying the rules from Mustang Gears MB, but I think that's exactly what they should do. When I first played and saw that you could cancel out of starting MB, the rules for Gears MB from Mustang was the first thing that popped in my mind.