I've used both and prefer newpipe, it's got a ton of features and has been more stable so far. From their github:
NewPipe does not use any Google framework libraries, nor the YouTube API. Websites are only parsed to fetch required info, so this app can be used on devices without Google services installed. Also, you don't need a YouTube account to use NewPipe, which is copylefted libre software.
Android? Newpipe
If you've just discovered newpipe, I would suggest trying vanced as well. It's good at limiting ads to 5 sec
I don't get any ads with vanced
I've used both and prefer newpipe, it's got a ton of features and has been more stable so far. From their github:
NewPipe does not use any Google framework libraries, nor the YouTube API. Websites are only parsed to fetch required info, so this app can be used on devices without Google services installed. Also, you don't need a YouTube account to use NewPipe, which is copylefted libre software.
https://github.com/TeamNewPipe/NewPipe