Ears though being a good measuring instruments are also prone to bias and other errors. I think a technical measurement would be very interesting.I have both the v3 and the bt20a pro and I think they are identical, except the bt20a pro has bass/treble tone controls and Bluetooth. I don't know if measurement would show a difference, but my ears can't hear any difference. I also can't think of any technical reason why there should be any difference but someone may correct me.
The only difference might be that you can do very limited room/speaker correction with the tone controls, but there are better ways to do that if it's important.
that said, if i may ask , why do you think they are the same? Did you open them up and compared ?
Cheers