I thought this may be an interesting debate. Recently I modded a Fostex T50rp and have been primarily using it instead of the Q701 I had been using. Now, comparing the two, it's obvious that between these two traits the T50rp wins in terms of accurate imaging, and the Q701 wins in terms of overall soundstage size, but mainly for it's width. The T50rp is a closed can so it's not as big and spacious sounding as the Q701, but the soundstage is more upfront and it's easier to pinpoint things on stage. The Q701 is big and wide and almost makes it sound as if the sounds are floating around you, but nothing is placed with pinpoint accuracy, and the width is definitely greater than the depth.
So the question is, which is more important? More accurate imaging and staging, or just a bigger soundstage size overall?