IMHO the choice of simple or complex depends on the customer you're aiming for. Reproduce their experience to make them feel at home.
Discount sales or auto parts, have you seen their retail stores? Shelves full of stuff everywhere, colors and signs screaming for attention, time sensitive deals.
High end boutiques are quiet, clean and simple, lots of space, crisp fonts, one product takes up your full attention, deals are way way in the back or in another location.