It mostly depends on the cost of the last mile (or last 5 miles). In a dense city, most of the last mile will be served by foot walking to a store which would

It mostly depends on the cost of the last mile (or last 5 miles). In a dense city, most of the last mile will be served by foot walking to a store which would have lower emissions (zero) compared to a delivery vehicle. In the suburbs, the last mile to a store will likely be a detour by car from wherever you wanted to be. So delivery probably has a smaller footprint than storefronts (since the delivery vehicle is likely doing deliveries nearby anyway).