OFC vs Busbar

[Dragonsyph]

I'm researching this subject in terms of Busbar vs High strand OFC.  

My question is does it travel over the top of the copper?  That's why you want high strand count wire because of more surface area?  

So wouldn't the current just travel on the outside of busbars?  And the whole inside is wasted?  Or am i missing something?

 

I guess if that's true, which has more surface area?  5200 strand 2 ot or a 1inch busbar?  

 

And then how much does the material of the busbar matter?    It is like buying OFC vs aluminum clad wire?