yewtube gives you 720p H.264, which your laptop almost certainly can decode in hardware.

YouTube gives you higher resolution VP9, which your laptop probably needs to decode with the CPU.

Install the h264ify extension to force youtube to give you H.264. You’ll be limited to 1080p.

Youtube has your computer run a shit ton of extra javascript code in addition to the video. Invidious has virtually none.

I’m probably wrong, but I think that’s the fault of a lot of crappy technologies running in the background on Youtube, things like blur (which is unnecessary) use the GPU of your system, while free instances like Piped or Invidious and front-ends like Freetube are as vanilla as possible, it’s just the video and some HTML (and Javascript? I don’t know).

Hardware acceleration.

Youtube is mining shitcoins with your computer

JS code execuction go brrrrrrrrrrrrrrr