Showing off is not bad in itself but it depends on your motives:

If you are trying show up someone else as being inferior to you then that is just being a smart-arse.

If you are accompanying someone else than you shouldn't try and outshine their performance.

Otherwise, if you are performing to others then what's wrong with a bit of showing off. It would be a pretty dull performance if you didn't. If you've got it, flaunt it.

DC