So which among the 3? I thk the 14 although focuses fast may produce a little distortion. Not sure if 17 or 20 or 25 wld be better. But the 20 suffers from slow AF.
Now that there should be a new 20mm f/1.7 announced about 12 hours from now, I think that could be my favourite lens. Maybe, it's fast enough to keep up with a baby.