% quoted are increases in stiffness.
The higher % figure is not necessarily 'better', as a high % increase in stiffness can produce a lot of oversteer and the handling become twitchy and snaps and bites hard (not what you want for an inexperienced driver)
TBH I would stick to the M3 items, as they're a safe compromise and at the end of the day oem items so it keeps the insurance guys happy also
