Not sure if by "efficient" you also mean it's better for the environment, but I did hear from some researcher that deliveries are ecologically much worse than going to the store. The podcast/"lecture"[1] is in Flemish (and audio/video isn't very accessible), so I'll translate the main reasons:
- Many disparate products moved to many individual homes (many to many makes for a lot of 'movements', fragmentation)
- 15-20% of people is not home during a delivery attempt (useless impact)
- Returns are equally bad (people order 8 pairs of shoes knowing they'll send 7 back)
- Different delivery companies cause even more fragmentation (driving to the same home)
Of course, you might just have meant efficiency of trucks as opposed to 2-ton cars occupied by single persons (assuming most people in NYC would do their shopping by car -- as a European, I can't imagine doing that in large cities' centres, but I do hear the USA is very car-oriented so I don't know how it is in NYC).