Originally Posted by
Fiery
As long as the bar is not too narrow, going wider won't really open your chest any further.
This is true.
Originally Posted by
Fiery
you use the diaphragm for efficient breathing, not the expansion of your upper chest
You don't know what you're talking about, so don't go there. Volumes have been written about correct and complete breathing. Your statement, in particular the part about chest expansion, is just plain wrong.
OP, unless you're having problems breathing, don't think about it too much.