A SF with a lp/p ratings of 50/50 or  a SF that is either 90/10 or 10/90.  All other factors being the same ... who would be the better scorer?

The 90/10 guy in most cases.

It depends what his other skills are. You mentioned all other factors being the same, but you can't really give an answer to your question unless we know what those factors are. If it's a guy that lacks speed and ballhandling, I'm going to want him to be strictly a perimeter shooter. If it's someone that's high in athleticism, but no speed and ballhandling skills, I'm going to want him close to the basket, therefore would go with the 10/90 guy.