MPV vs VLC - AVC1 CPU usage with GM45

I'm using an old laptop with the Intel GM45 chipset, running Artix.

Playing H.264 1080p 60fps

By default MPV uses gpu x11egl. Playback is very choppy, unbearable. Using --profile=fast makes it a lot better, still not perfect though but almost there. The CPU usage goes up to 100% and stays above 75% all the time. -vo xv results in the same high CPU usage.

On the other hand, using VLC with the default config the CPU usage is within 40-72%. Much lower than MPV, consistently, and playback is 100% smooth.

Based on the -vv output, it seems that it's also using elg_x11.

So why such high CPU usage with MPV, why does it struggle? Can MPV be tweaked to work correctly/faster with x11egl consuming less CPU, like VLC does?