B&H is the best. Their search and overall UI is great, their browsing taxonomy is incredible (especially when you're looking for something in their wheelhouse; if you're shopping for, say, a very specific type of camera lens, it's effortless to narrow to exactly the choices you want), and on top of all that, they're usually price-competitive with Amazon.

Their closing on orthodox Jewish holidays takes a bit of getting used to, but I just consider it part of the brand now.