The advantage of standing meditation is that you have to have more awareness of the body, so that there can be more balance between awareness and concentration. Sometimes in sitting the concentration may not have the body awareness, the concentration may get a little bit too deep without the awareness to support it Some people may even fall into sleepiness or sloth at that particular time because of the lack of awareness, or particularly if we are trying to develop more wisdom, it just falls into tranquility, without perhaps developing any wisdom at that time. Not that tranquility has anything wrong with it, you may want more tranquility at that time. However, it is better to have tranquility balanced with awareness than just have concentration into excess, for the practice of Vipassana meditation.
In the sitting meditation, because it is usually more comfortable for people, often they can sit and not worry so much about having to keep their body upright, which is energizing. But standing meditation is very helpful for people who are having a lot of sloth and torpor because it actually is energizing. Even though it uses energy, it does energize, because of the fact of body awareness. Yes, it is very helpful to do standing meditation while you are standing in line for anything, otherwise you may get impatient. So there are many situations in life where standing meditation is very helpful for us.