From my POV, an adblocker's perceived quality is primarily weighted on whether it can block visible ads without impacting performance. While uBO on firefox is a more capable blocker, I honestly don't browse enough sites to know one where uBOL provides a worse experience in this metric than uBO.

I prefer vivaldi's UX to firefox enough that i am willing to settle for technically-worse adblocking. If I notice this becoming practically-worse, I will consider switching.