All of that. Lack of ads, more performant etc. Plus (and depending on the device), you can set it up in such a way that you don’t need to sign into your google account, yet still have ability to watch YouTube (Smartube), install apps (side load plus use the Fdroid TV store … name escapes me at the moment… Flicky I think?).
Even if you need to be signed in for some reason, it’s a smoother experience.
Its just…better. You’ll lose some of the prettiness (for some reason, mine no longer displays backgrounds from upsplash, only solid colours) but its more than worth it.
EDIT: Yes, it IS Flicky
f-droid.org/packages/app.flicky/