I had previously trained with a stages left only power meter without issue. I think as long as that is the only power meter you use, they are consistent and that is all that matters. However, I upgraded my crank and got a Quarq Dzero, and noticed consistently lower power than my stages, which was a little frustrating.
I have also just purchased Assioma Uno pedals for my new TT bike, and also, this is reading around 10% higher than my Quarq Dzero. In my case, I am convinced that it is because I am left leg dominant. I have a stronger left leg than my right, and although according to my Quarq, my power balance is pretty even, the Quarq does not really read both sides, it just estimates based on the area of the pedal stroke that the power is applied. There is a youtube video in which a quarq ‘dual sided’ meter is compared to power pedals and it is clear that the quarq reads power on both pedals, even when only one pedal is clipped in and the power pedals are reading 100 / 0 on the balance.
Due to this discrepancy, I have just ordered the upgrade pedal from Assioma, and hopefully this will confirm my theory that my left leg is more dominant and this will even up the mismatch between my pedals and Quarq. (even though I would love to have an FTP of 330 rather than 300, I don’t buy it).
So in answer to the thread, do I regret having single sided power, yes, but only because I also have another power meter on another bike that does not compare accurately. I am leaning towards using my Assiomas on all my bikes and selling the Quarq to have consistent power between bikes / indoor trainers.
As others have said, if you only have one power meter and it is single sided, it is perfectly fine and I was happy with my stages for 3 years when I just had one bike.