I have the Favero Assioma Duo pedals and could not be happier. It also allows me to transfer them to my spare bike or road bike, so I'm always training on the same powermeter.
One of my coaches is the big data nerd for WKO+ (who helps them develop metrics etc) and he's really happy with the reliability of data we're getting from them on the track.
ETA: I use straps (BLS velcro) and put out 1700w peaks (1550w 5sec).
From everything I've heard, Stages is pretty useless for trackies, especially sprinters. Sprinters have very different needs than enduro riders.
FWIW, Assioma's max out around 190rpm or so, so if you want really reliable cadence measurements over that, also use a cadence sensor.