Is a curved bread lame better or a straight bread lame?

It seems to me that curved blade evolved as the common form because it seems to facilitate an ”undercut” rather than a straight downward slice. Undercut always seems better with lean dough breads but straight is quite acceptable for richer dough breads. 

I am guessing that it was simply easier to make the curved one than the straight one.  Take a razor blade and thread it onto a stick. And so a tradition is born. BTW if you are making your own, next time you change the wiper blades on your car, save the metal inserts that give them rigidity.  They fit a razor blade perfectly.