there are some who are gifted with memory for words. I am not one of them.
I can remember tunes forever.
in the movies,
there are many well-known actors who use a crib sheet and can turn out a convincing
performance.

I don't agree that memorizing words automatically makes for a good performance.
I don't agree that reading from printed material does either.

If you do one style of music, it's easier to memorise without words in front of you,
however if you do a lot of different types of songs, then this is not easier.

I think you can do both depending on the situation. Even recording artists often
have words in front of them and can be convincing in their performance.

You can't generalize because it changes from performer to performer.

Frank