Personally I would prefer someone to use words rather than try to bumble through a song from memory and end up forgetting the last verse or leaving one out.

I do actually try to learn words and have sort of accepted it as a challenge being now post 60. The first few times use words to establish key/check audience response.

The one thing I can't do is use words and try to sing through a mike - I have to do that from memory - the "bear of little brain" can't handle that aspect on multi-tasking.