I once heard a philosopher(sp?) give a speach.
he started to talk about this issue (on paintings, but that doesn't matter).
he started with a claim: "there is only ONE size for an image! And that is the right one!"....
obviously one might think. But then he explained. So many times we see an image, and think "I wish this was smaller" - "I wish he would crop this" - "oooohh - If only this was bigger than life..."
in his words: the true artist makes the right size for the right image.
this doesn't help you here, but as photographers we have the advantage of trying different sizes before we make our desicion..
I'd do as mentioned before. different formats (I really hate photographic exhibitions where every image has the same size and framing - and all is on a straight line...)
for your image in question, I can't (obviously) help you.
If you make different prints in different sizes, I am sure the answer will come to you. You'll know when you see it.