I have both the 40mm FLE and the SWC. I used to have an XPan with 45 and 30mm lenses. What I found was that although high aspect ratios may work well for motion picture processes such as Panavision, where there is horizontal action to be included in the frame, they are not ideal for most still compositions. I'm a fan of wide-screen high aspect ratio presentation, but only up to a point. I found that the XPan aspect ratio is simply too wide for good composition: not always, but most of the time. I have it in mind to write my thoughts about aspect ratio for the "philosophy of photography" forum.
I think that still pictures, for me at least, when presented in a wide format, are at their best at an aspect ratio that does not exceed 2:1. The XPan is much wider than that. But I can crop pictures from the 6x6 and 645 images I take with my 500C/M. The 40mm lens is about equivalent to a 25mm in 135 format. That's often wide enough. If I had a 30mm fisheye, I would probably use it for a few shots, but I don't think I want that curvilinear perspective much of the time (Besides, my outfit is already as bulky and heavy as I can manage).
I compose in-camera for my 2:1 aspect ratio by having 2:1 safe area lines marked on the viewing screen. I don't crop previously taken shots as an afterthought. I do the same thing with the viewing screens on my Nikons.
Using my Hasselblad PCP-80 projector, I project these shots on a large screen, masked to the 2:1 ratio. That's an important reason for not using the XPan: it takes a 65mm wide film, only 54mm of which can fit in the slide mount.
When I had the XPan, I found that the 45mm lens did not cover enough for me in the vertical plane. The 30mm lens does, but was usually too wide horizontally!
So these are the reasons why I use the 500C/M in preference to the XPan. I don't use the SWC much for my wide-screen shots, but I love it for black-and-white work!
