Participating preferred lets investors collect their preference amount AND participate alongside common in the remaining exit proceeds. This 'double dip' is most punitive in moderate exits and least relevant in very large ones. Caps on participation (e.g. 3× cap) limit the dip to a multiple of the original investment.
Participating preferred is more common in down markets, late-stage rounds, and geographies where founder protections are weaker. In US early-stage, 1× non-participating is the modern default; participating preferred should be a deliberate trade.