If I want to ascend a rope with minimal equipment, I use 2 Prusiks: one tied to my harness, and the second one for my foot.
However, there are two ways to arrange the Prusiks on the rope - the foot below the chest, and the opposite way. The first arrangement is most intuitive and described and in all places on the Internet I looked, e.g. here. Also, this site tells that it's the right arrangement:
Notice that the waist Prusik (E) is above the foot Prusik (F)
but doesn't explain why.
When we practiced crevasse self-rescue, I noticed that my friend used the second "counter-intuitive" way; he said that he always used it, while I always used the "normal" arrangement. I tried the "opposite" arrangement, and it worked marginally better: I could ascend a bit higher each time I extended my leg (this might have been by luck). One difference I noticed is that you have to choose the length of the Prusiks carefully (use a long one for the foot) in order to avoid getting stuck. Otherwise, the arrangements seemed pretty similar.
Is there any reason to choose one arrangement or the other? Should my choice be different in different situations? (assuming I have Prusiks of any length)
P.S. I am not talking specifically about crevasse rescue.