The Panasonic LX3 and the Canon G10 are both superb cameras in their own way. These are high-end point-and-shoot cameras aimed at photographers who need a pocket camera to complement their dSLR. But I got a LX3 over the G10. It's my first Lumix, and I'm extremely pleased with my purchase.
Here's why I chose the LX3 over the G10:
1) The G10 shoots at 15 megapixels, while the LX3 shoots at only 10. I do not need that extra resolution, as I will never be printing images from a pocket camera to such as huge size. Those extra pixels will only serve to slow down my post-processing with the larger file size. Besides that, 15MP crammed onto such a tiny sensor is going to have its consequences. The pixel pitch is much smaller than the LX3's, and therefore, noise performance is slightly worst than the LX3's. But with both these cameras, anything above ISO 800 is only for emergency.
2) The LX3 is smaller in size than the G10. If I'm going to buy a compact camera, it better be small enough to carry around, thus my choice with the LX3. The G10 is heavier and heftier, but the advantage is it offers better grip (obviously).
3) The LX3 is cheaper than the G10, by about $100.
4) The LX3 has a wider and faster lens than the G10. On 35mm equivalent, the LX3 has a 24-60mm f2.0-2.8 lens, while the G10 has a 28-140mm f2.8-4.7 lens. An f2 lens, coupled with image stabiliser, will mean I can get faster shutter speeds on the LX3 than on the G10, and this is just what I need in low-light situations. Furthermore, the 24mm wide angle is an advantage when taking group shots, and is nice to have in landscape photography too. The compromise is that the LX3 only has a 2.5X optical zoom, and doesn't have as far a reach compared to the Canon. But that's fine for me: most of the time I'm doing wide-angle stuff. Your decision will vary according to your shooting needs.
5) LX3 does incredibly good HD video (1280x720 @ 30fps). The G10 on the other hand only does mediocre 640x480 video. The downside is that video on the LX3 is stored as Quicktime motion JPG, which is an aging format, and file sizes tend to be huge. But still, the quality is stunning!
6) LX3 has a switch dedicated to changing aspect ratios - 4:3, 3:2 or 16:9. The cool thing is that in any aspect ratio, the same angle of view is maintained. As a result, you make the most of the sensor's area, getting similar pixel counts in all modes.
7) The LX3 has some really cool scene modes, notably the film grain mode, which simulates B&W film images, and also the pinhole mode, which simulates pinhole images with strong vignetting.
8) The LX3 shoots up to ISO 3200; the G10 only goes up to a max of ISO 1600. Sadly, ISO 3200 on the LX3 is anything but usable. Still, it's an advantage over the Canon.