The XA is smaller, "full frame", and truly (comfortably) pocketable. No camera that doesn't have either a retractable lens or a clam shell design like the XA is truly pocketable - regarless of size, at least not comfortably. This is why, while I'm sure the X100 is a fine camera, I would never consider it for purchase and why I would take any of the compact APS-C DSLRs by Nikon, Pentax, or Canon (etc) over the X100. They're a much better bang for the buck, and take other lenses/focal lengths. For me, a nice fast 35mm prime (50mm), an extra charged battery, a UV filter to protect the lens (optional), lens cleaning kit (in case of emergency), and an inexpensive "sling bag" is the way to go for traveling light...
The X100 is a very good deal for a fast/excellent 35mm focal length attached to a very good "portable" camera. If I didn't prefer 50mm (which is what I shoot with 90% of the time...), and shot with a 35mm 90% of the time instead - I'd probably be saving my pennies for an X100.
NOT knocking this camera. But I think people who are seeking "pocketability" in any camera where the lens juts out - even a pancake lens, will likely find it doesn't suit their needs.
XA - an excellent choice for a "full frame" film camera "in your pocket"...
Compact DSLR + prime + small sling bag = best "bang for the buck" travel light set-up for higher quality shots.
X100 - excellent small camera (but not pocketable) with a wicked f2/35mm lens, a good deal for an expensive optic with a pretty decent body permanently attached.
Any "compact, pocketable superzoom" with a minimum 10X zoom + a Flip Bak attached to LCD - best pocketable "carry with you anywhere" camera set-up. (An underrated tool and a "must have" imo).
