Best is so subjective. I'm trying to decide on the metal for my own band but considering Tungsten. Seems very strong, scratch resistant, still has weight (which I want) and its cheap.
Plus in my case I want a brush finish that is a little darker (similar to my watch below). I might do a thin channel that is high polished so it looks more white, offset to one side.
Titanium...that has the "danger" of being hard to remove in the event you injure your finger and it swells, right?