The XA3 is the same as the XA2. They just added DX and a couple other minor features. The XA4 has both the 28mm lens and the macro (pretty much a freebie with a 28mm lens). The XA1 is a great camera. The soul of a Trip in the body of an XA. It uses a selenium cell so it never needs batteries. You only get two ASA settings (100 and 400) and it is fixed focus. But neither of these are big drawbacks for a pocket camera.
Originally Posted by Someonenameddavid
The three smallest 35mm full frame cameras are the XA's, the Stylus and the Minox. Although individual dimensions vary (e.g. the Minox is taller, but not as thick when closed) they are essentially the same volume. The Minox is a classic clamshell design, so it is much bigger with the lens door open and the lens pulled out. The Minox also has a shoe on top, so it can snag on a pocket. Both the XA's and Stylus use Olympus' classic "sliding dust barrier" so they are the same size opened as closed. With the Stylus you also get a built in flash.
I haven't had the best of luck with the Minox shutters as they get older. The Olympus' seem much more dependable, as befits a camera built by the gods.