There are two main types of liquidation preferences. First Participating vs. Non-Participating. Best for us (VCs) (worse for founders): Participating Preferred (i.e. VCs get our liquidation preferences PLUS we "double dip" and share pro-rate in anything above). Non-participating means basically that we take our pick: either the Liquidation Preference (usually amount VCs invested, sometimes though 2x or 3x etc.) or share pro-rate as if we had converted to common. So we take our pick of the higher amount
Participating Preferred: We get best of both worlds.