Rating: 5 / 5
I've used the Black Diamond ATC-XP for climbing and rappelling and figure8s for rappelling. I recently decided to try the Petzl Pirana.
The Pirana weighs 96grams versus the ATC-XP at 89grams (my measured weights). If you are "canyoneering", as I sometimes do at parks like Zion, I LOVE the Pirana.
The Pirana is always connected to the carabiner. You don't connect it or disconnect it to rope up. It is easy to change the amount of friction affecting the rate of descent. It is also much faster and easier to connect the rope. Larger diameter ropes can be very hard to bend to get loops inserted into the ATC-XP. Connecting the rope to the Pirana is very quick for a wide range of rope diameters.
There are options for wrapping the rope around the pirana to stop the descent.
The price is much higher than the ATC-XP or a figure8 but it is definitely my favorite rappel device for canyoneering from now on.