Peene,
The Suunto does have a foot pod for run speed and mileage as part of its accessory line, along with a skewer pick-up and cadence pod for bike functions in their Traithlon pack. GPS is additional. But you're right, unlike the Polar RS800CX Multi, it does not measure actual cadence and stride length. At least now with the 310XT, there's another option for triathletes, that has GPS built-in rather than another module to mess with.
ANT seems to have the advantage of higher range from the signal source to pick up the data. On Polar cycling sensors you have to open the front fork module and reconfigure the internal switches to boost its power output, if you plan on wearing the watch on your wrist rather than mounted on the handle bars. I believe ANT is the same system the teams are using on the Tour de France to give real time feedback to the coaches and tacticians? I also like Suunto's Team Pod for monitoring up to 50 athletes at a time. Great for indoor cycling classes or track workouts, and more economical than Polar.
Looking at the Quarq Cinco for power metering, the warning would be that its measurement is combined output of both legs versus each leg. Same goes for the Ergomo system.
Jeez, my Geek is showing!