TZ all day and twice on Sundays. Met is one of Stern's better games in the last few years, but it doesn't hold a candle to TZ. Which nine out of ten people will tell you is one of the (if not the) greatest pins of all time.
That said TZ is a fairly deep game and is more of a stop and go game. Metallica is much faster and is focused on flow. Neither game is for everyone and if you've put a decent amount of time on either, it will become clear which one is for you.