The song you pick as the single…
How are you going to play it live?
What about when you only get to play one song…for a showcase or in a meeting room?
What about when you only get to play that one song amidst a bunch of other artists playing one song?
What if you have to play for an audience in the morning?
How will it translate best on TV or video?
If it becomes a hit, how does it best fit in your set? Can you close with it?
When the song is being played and performed at its best, what is the audience doing, how are they responding?
If the answer to any of these questions is ‘I don’t know’, it’s not a reason to not pick the song as the single. What it tells you is you have some fun problems to solve if you want to have more fun with your song.