[My English Castle]

I think you need to work out a satisfying combination of the two,
Most folks here will advocate a price book so you can see what a good sale price is--then you supplement that good sale price with your coupons.

It also depends on the expiration date. Most coupons are good for at least a month. Try filing them and cross matching them with sales, Then yell "Bingo" loud enough for all of us to hear when that happens!