I try to avoid AP whenever possible as their salespersons will always try to raise the prices if they think you're an easy target. For CP, the prices that all staff quote only vary ~$20 max, and the salesperson might even put in filters/accessories FOC if you're buying large amount of goods
Whichever shop you go to be it AP or CP, you still need to do your homework, find out the prices and all. With the internet, it's not too difficult to find out whether things are overpriced here and that includes the ACCESSORIES, especially those 3rd party ones.
Also, my recommendation is to stick to 1-2 salesperson that you're comfortable with and the guys I deal with know better not to play me out. Also, go on the days when it's not crowded (avoid Saturdays).