I'm using the RC3 GPS & S3+ Stride sensor together for quite a while. My experience is:
a) It has to be calibrated for your running style and shoes!!!. If you change this, you have to recalibrate it. I do the calibration for mine during my 60% of the training typical runs (Basic Run, one hour, 8k ,75% HRmax). Once calibrated it works fine.
b) I'm doing my runs in quite different terrains (forrest, dirt roads, flat street, hilly terrain). I upload all my run to PPT and to Strava. In PPT the distance is calculated from the Stride-Sensor, in STRAVA from GPS data. The difference between the values is normally somewhere around a 100 meters for a 10k run. But keep in mind GPS measured tracks have an error, too (calculation is taking "shortcuts" between two waypoints). When I run the same tracks (with different paces, intervals etc.) the stride sensor distance is consistently the same (within a range) whereas the GPS distance is not so consistent.
c) recently I did a 10k run on a officially measured track, the GPS calculated distance was 9700, the "Stride-Sensor" distance was 10.050m. (And I did no recalibration of the stride sensor for my race pace)
d) From my view the advantages of using Stride-Sensor data over the GPS data (and that's why it the chosen default behaviour of Polar, I think):
- its more reliable, GPS Signals often get inaccurate if running in cities with high building or dense forest.
- You get instant pace & speed data. When I only had the GPS pace it was quite hard to run for a specific pace because it was always quite jumpy, with the stride sensor the pace reacts more instantly.
- If you do for example track session (400m circles) GPS distance will be completely messed up, while stride sensor distance is still ok.
e) And finally, yes I am missing the instant cadence view during the training, too.
Hope this helps!
Polar Equipment: V800 & H7 & S3+BTLE, RC3 GPS (Black NOW with altitude) + CS Cadence Sensor + s3+ stride sensor, F11 (not used anymore)
Sports: Running, Cycling, MTB, Downhill / Freeride, Hiking, Climbing
Toys: Wildsau Hardride (MTB-DH), GT Zaskar LE (CC), Rocky Mountain Bonandrini Edition (Dirt Bike)