I'm trying to decide between buying a Sigma 30mm F1.4, or spending on almost identical amount of money on a Canon S90 compact. I really want a better small camera to have with me all the time, but I also really want a better indoors available light tool. My primary subjects are my two kids, ages 2 & 4, often indoors at night. I usually prefer not to use a flash.

Here are my reasons for going from my current 50 F1.8 to the Sigma 30 F1.4, and I would appreciate any feedback, particularly from someone who has done this with an APS-C camera (I have a 450D, aka XSi).

1. Wider angle. The Canon is effectively an 80mm short telephoto on my crop DSLR, and I can't back up enough to get everything I want in the photo from some angles. I'm really liking the idea of going to an effective 48, when I frame with my short zoom at 50 it seems to open up so much more.

2. Faster Lens. The 2/3 stop would be very useful, I currently often shoot 1600 ISO at 1.8 and EC -1, pulling it back in RAW, to get it to 1/240 or 1/320 for a moving kid, and would love a bit more speed, which I would use for shutter speed, ISO or stopping it down for a little better lens performance, depending on the situation.

3. Increased DOF wide open. At eight feet, which is a common shooting distance in the living room, my DOF is 6 inches with the 50 at F1.8. Add in a moving kid, the AF not being top of the line in either the 450D or the 50 F1.8, and sometimes my keeper rate isn't so hot. According to the on-line DOF calculator website, even at F1.4, the DOF for the 30 mm at eight feet would be 14 inches, would should hugely add to the chances of being in focus with a moving kid indoors.

4. Is the AF itself better on the Sigma 30 F1.4 than the Canon F1.8?

5. Better bokeh with 8 blades instead of 5.

On the other hand, I am truly lusting after that S90 combination of a F2.0 lens, with RAW, full manual controls, and improved high ISO performance in a genuine shirt pocket compact form...

Any comments would be greatly appreciated!