I disagree with 20 pre > 19 pre by a slight amount. 20 noted how 19 gained a whole lot of power after absorbing Goku's KMHMH, while still not being too worried and being just like "how greed you are".
Goku was already pretty fucked when #19 absorbed his base power. He couldn't even get up for himself:
Not to mention it has barely made a difference according to Vegeta, since he judged #19's power according to his
movements and he didn't make any of it after absorbing Goku's base power. After analyzing #19 post Goku base power, Vegeta just notes how his estimations were accurate, showing #19 post base Goku >= #19 post KMHMH.
Piccolo also said they can fight in burst and that, therefore, the energy 20 absorbed was nothing. It could just mean it was nothing compared to his full power, not that it barely added an increase on the androids' power.
There's plenty of evidence for 20 post > 19 post p, just like I showed in my previous post. The same Vegeta who ripped 19's head off had to make bluff against 20. Even if Vegeta did lose energy after firing the BBA, the main cause of him being weakened was #19's absorptions, as noted by Piccolo: