My synopsis of the Mastermind series:
Original: Rolly, even - great ball for staying straighter for med/heavy fresher lanes
Genius: Weaker version of the original
Intellect: Great for staying straighter on heavy flat patterns
Scholar: Sharpest off the breakpoint, a little too responsive for me on most surfaces
Einstein: Benchmark of the series - perfect blend between Brainiac/Strategy
Brainiac: Similar length to Scholar but much more predictable downlane
Strategy: Slightly stronger version of the original - for med/heavy fresh lanes
My favorites are the Brainiac and Einstein, which split the difference between my tanks (Grudges, Gurus) and midrange equipment