I'd suggest using the app over the mobile website. If you are in store, it will tell you where in the store the items are (Bay and Aisle) which is super useful.
The Home Depot mobile app is pretty nice. It's significantly easier and faster to use, especially while in a store. Along with the quick location toggles/searches, it's worth checking out.
(I tend to eschew apps however much I can. But maybe I should just suck it up until this project is done.)