For me, it's usually availability as a deciding factor. Many of the things I end up buying from there I am not able to obtain locally unless I drive a fair distance out of my way. Otherwise, I do my best to buy from local stores. As such, I just returned from my weekly grocery trip a short while ago.
Usually, I always buy clothes and footwear from a local store - even if it's out of my way. Earlier this week I drove an hour in one direction to go to a men's clothing store to purchase a tuxedo, a new white shirt, and another sport coat. These are things that I would never buy online. But things like blue jeans, I will order online as those are less critical for fit and style.