I have the S12, I exclusively pumped with my first and BF and pumping with my second. I get similar with the S12 as I did with the medela symphony. Two things make sure you get the right flange size (you can buy measures and inserts for the pump the standard it comes with is 24mm which is quite big) and I have had to have the motors replaced twice. Momcozy are very good at providing replacements with extended warranty but it can’t take 9 days for a replacement to get to you. On the pumping support groups this is common across the Momcozy range.
I have the M9 and it empties me pretty good! The suction is really strong so I definitely recommend it.
I really like the V1 pro
I have the S9 pro and definitely recommend it