I feel Android 20 held the edge in base power, but Android 19 was able to narrow that gap and take the lead after taking energy from Goku and Vegeta respectively. Meaning, Goku's energy was enough to put him a notch below his creator, and Vegeta's energy pushed him right past said caliber. That said, any gap that Android 19 acquired over Android 20 was likely closed when the latter himself had the opportunity to obtain energy.
A little power comparison pertaining to these two:
Android 20 (post) > Android 19 (post Vegeta) > Android 20 (pre) > / = Android 19 (post Goku)