Not only is it faster, but it's so much easier. The last time I purchased a tourist SIM (not top-off) intown the first person had no idea how to install it and it took the second person forever. At the airport they do it quickly because they do so many of them and if there is a problem there are a half dozen other clerks to help out. One time I got stuck behind a large Korean tour group, so I just moved over to the next counter and was out in seconds.