I own one Sony xr500, same spec as 520 except hdd is different size (120GB vs 240G)
Dim light - Good, better than CANON i think, has night shot (for fun)
Optical Stablizer - extremely good. you can walk and shoot, footage is usable (i downloaded a CANON footage captured by HSF100, optical stabilizer is nowhere close to SONY), CANON footage is shaking (compared with XR500 same scene same camera man).
lot of review saying that CANON color is a bit better than SONY, but brother i tell you, if you handheld your camera and shooting while walking, good OPTICAL STABILIZER is much much more important than color (and color also subjective), shaking footage is useless.
useless footage is useless.