PowerLine uses very similar technology as WiFi does, except that power cables are significantly more noisy than air. As such, they usually perform significantly worse than wifi. With exception of certain cases like buildings with 19th century 2m thick walls.
In most other cases, quality WiFi equipment performed better and was more stable.
This has been my experience. I bought some Devolo powerline adapters a few years ago to try in my apartment, and got quite poor speed (<100Mbps) and network was rather unstable. Switched to WiFi and got better speed and stability.
Last year I moved to a new place and faced the same issue of wanting internet in a different room and tried the Devolos again. Same experience except worse speed. Again I had to fall back to WiFi, which at least gets me ~150Mbps here.
That depends on where you are. In a drywall or wooden house, this would be true, but in concrete apartment building with thick walls and many other networks, it might not be the case.
In most other cases, quality WiFi equipment performed better and was more stable.