Can't speak to AAP as they don't have much of a presence here.
Autozone is best for me, BUT their emailed coupons NEVER worked for me in-store even though they VERY clearly said "online or in-store." I tried contacting corporate and just got the runaround from a know-nothing. I blocked their emails and sent them all to spam after awhile.
The key with AZ is trying for multiple purchases just at $20 or more.