Well I would say that if you are telling someone your PR then of course you'd count the weight of the bar. Otherwise in your record keeping it doesn't matter unless you live in a part of the universe where the weight of objects changes everyday
The weight of the bar simply "factors out".
So yes it's personal preference. I tend not to count the weight of the bar as a rule simply so I won't get confused when I look back over my logs and wondering whether I counted the bar on certain things...but I'm old and senile.