vanced is just the normal youtube app with just some modifications to block ads and background playback. It is closed sourced, not to mention, and uses a modified version of MicroG that works in unknown ways to access/sync with the google account, which is very different to the original MicroG (which has been developed to replace Google Services from your phone to minimize google tracking your activities.) . If you don't want unknown apps get access to your google account or if you care about your privacy/security, don't use Vanced, stick with NewPipe.
But I agree that if you have sensitive data on your google account you should make a value judgement yourself on if the extra convenience/features on Vanced is worth the risk over NewPipe.
I personally use a different mail provider so I don't have much sensitive information on my Google account, basically just using it for YouTube and Play Store.
