Simon Joinson has the following conclusion on the JPG photo output quality from both cameras:
The 500D's JPEG output is a lot closer to the EP-1's, but even here the little Olympus has the edge when it comes to pixel-level sharpness – despite the Canon's higher nominal resolution. There's really not a lot in it though, and in a print you'd be unlikely to see any difference in detail at all. The 500D's color and contrast is a little more muted, and again it's handling the roll-off of highlights a little more gently (and again, the difference would be less at ISO 200), but as both cameras offer extensive control over image parameters this is really only relevant to those who never change a single camera setting.
Lenses used were the Olympus 50mm f/2.0 Telephoto Macro ED on the E-P1, and Canon EF 50mm f1.4 USM Standard / Medium Telephoto on the T1i / 500D / Kiss X3.