Well, I can't offer comparisons because I've never used the Canon Xl2s. Come to think of it I;ve hardly used my nice new Sony HDR-FX1E either as yet
But here was my line of reasoning for choosing the Sony, and a few other points of possible interest that might help you decide.
Till now I've used my trusty old (well not that old) Sony TRV33E which I'm very happy with so I already know and like the Sony brand. I was ready for a better camera - something in the Prosumer range. the timing was right for the Sony when it was released this year and so I thought I would future proof myself and get an HDV camera.
The Canon costs over a £1000 (UKP) more than the Sony. That I guess was a plus for the Sony. However, the Sony does not have native XLR inputs for microphones. Not a plus point, but for about another £150 I got myself a Beachtek box to put between the camera and the external mics and now I can happily use my Sennheiser ME66 microphone through that.
Not too much of a problem for me and the stuff I shoot but, from memory, the Sony is not as good in low light conditions as the Canon. Also, the Canon has interchangeable lenses. But as (just) a keen hobbyist, it's not likely I would ever purchase further lenses so this did not prove to be a plus point for me.
Offhand, I'm not sure if the Canon has a true widescreen mode. Marc? I know the Sony does and this is what I want.
The bottom line for me is that the canon costs half as much again as the Sony and I couldn't justify the extra for what might be a slightly 'better' camera in SD mode. Add to this that the Sony is a bit more future proofed with its HDV capability and I would have enough money left over to buy a new tripod, microphone, case, light, headphones....... I got the Sony.
I've hardly pushed to the edge of the envelope but I'm VERY happy with it so far.