All stations will have price variations. BP generally does have higher gas prices here in Northern Virginia, but it's generally not too far off from the prices other stations are charging.
Around here the price topper generally seems to be Shell, which is normally 20 or so cents a gallon more expensive than the other stations around it.
But, I generally fill up at Shell. Not because I'm Shell loyal, but because my grocery store has a rewards program with them. My last fill up I got $1.20 off a gallon.
When I'm just topping up, or in between points based fill ups, I'll generally get gas at the Global or the Wawa.