Do you wander when you go shopping, or are you focused on a prepared list?
It kind of depends really. If I do go in with a list of things I need to buy then it usually means that I will not stray too much and spend more money that I intend to. Having a list makes you more organised and I have found that I spend less time wandering aimlessly in the various aisles that way.
Therefore that can be very useful and better for you when you do not have a lot of time to get your shopping done. Now, suppose you have some time to kill and are in no particular hurry to get your grocery shopping done. Well wander around and check the various shelves for new and interesting stuff that you have wanted to try or things that you have never seen yet but would now love to try out. There is a certain joy in finding something new and exciting and you can’t wait to try it as soon as you reach home.
So it depends on you and your schedule really. I find it helpful to keep a list handy but when you have some time keep perusing the aisles just in case you find something tasty and interesting.