The PPQ is nothing more than a permantly cocked P99, with the trigger pulled-back to where it makes that click sound.
I traded my PPQ for a P99 because I can de-cock the P99 and not have to worry about something snagging the trigger.
Examples: The beads on a windbreaker while holstering a PPQ.
With the P99, you can de-cock it and stuff it down your pants without about blowing-off your hootis, plus the P99 has 1 small weaver rail, vs the PPQ picatinny cheese grater which snags on things.
You can put a decocked P99 in your wifes purse or the console of you car and not have to worry about a key-ring or something pulling the trigger.
The PPQ must be holstered at all times.
FWIW the single-action trigger on my P99 is about a pound lighter than my old PPQ. The trigger re-set is identicle on both guns.