My 2 cents:

I only race 70.3 and IM. I own an assioma UNO and i train really a lot indoor with a trainer with a good owermeter.

I always have 2 PM in my session (assioma + trianer) so i always compare the 2 graph.
I know that my left leg is the dominating one and thx to the double PM in my session i know weel how my leg are balanced during my rides:

IN lower Z2 and Z1 my left leg produce something like 46/47% of the total power. When i'm in upper Z2 or Z3 they are pretty balanced and when i go over LT my left leg start to push more watt than the other one.

My opinion is that if some has a trainer with a good PM indoor (Drivo, direto; neo, kickr) a UNO is pretty good.

What if I only have Bluetooth smart with my Polar Vantage V. Will it handle both pedals? Or only average both of them?

I'll throw in my own experience of SS PMs.

I have a Quarq and an elite direto. Earlier this year I was given a stages on the cheap, so transferred the quarq to the TT bike and put the stages on the road bike. I did this just before the season started. All my historical power data is on the quarq.

I have 57:43 imbalance according to my Quarq.

Now when I started to use the stages- yes the initial 'average power' in a ride would be fine- but other metrics were not.

FTP measured on quarq: 245 watts
FTP on Direto: 239 watts
FTP on stages: 269 watts

I don't have my 3 second and 10 second power analysis (important for road cyclists) handy but I recall the difference was also big- almost 100 watts for the shorter time durations And that is huge.

So to me- the stages on my road bike is not very useful. Ok- it gives me a ballpark figure of the power- but not much else. I can't compare stages data to my old data in any meaningful way to see if I've progressed. If I compared to the direto- it overreports by 30 watts. How do you train with 2 sets of conflicting numbers?

The thing is, economically- why would you buy SS when there are DS options that are not much more expensive? An FSA powerbox or Power2max NGeco street price is within $100 of a stages or a 4iii? Why buy an inferior product?