The DC10 shoots in SD. Nuff said. It is low resolution and has a lot of compression artifacts which are painfully obvious on any sort of modern display. It was a big disappointment for me.
The main problem with the S10 is that it shoots natively in interlaced video. While this is not an issue on a TV set (which typically can deal properly with those sorts of inputs), it is a problem for viewing on a monitor. Images reconstituted as progressive frames are actually two images superimposed. Not a problem for static scenes, but any sort of rapid motion causes stutter on a monitor as a result. Footage recorded natively as progressive does not have this problem, so clips from my G30 and T3i would be smooth on a monitor.
The other problem with the S10 is that it does not have a full manual mode, there is only automatic and semiautomatic. That limits how you can shoot. I prefer having full manual control over parameters affecting exposure.
The S10 also appears to use a more primitive encoding algorithm than the G30 as well. A freeze-frame from the S10 typically looks like an impressionist painting, while one from the G30 looks like a photo. The image generated by the G30 is overall a more refined one than that produced by the S10. When I first got my G30 I shot a series of clips of essentially the same thing using the G30, the S10 and the T3i. Both the G30 and S10 were a lot better than the T3i, with the G30 somewhat better than the S10, but not massively so.
The S10 has more pronounced lens chromatic aberration than the G30. The purple blooming seen in parts of the image at high contrast boundaries is caused by light scattering on the sensor surface. By its nature it is a phenomena that will be more pronounced with small sensors, so you see it with both the S10 and G30, but not the T3i. The RX100 has almost none (although there is a bit, but it has much smaller dimensions than the two Canon camcorders).
The S10 has a higher resolution sensor (and so does the DC10, relative to its video resolution), but that does not translate into better overall resolution. The G30 has a noticeably improved image in that regard, but it is still quite a bit lower than the nominal 1080 lines you should get for HD. Most likely they are skipping lines in the S10 and DC10 in the sensor read.
The RX100M3 video appears to satisfy most of my criteria in terms of what I expect from HD. The only two things I miss from the G30 are the massive zoom range that camcorder has, and the robust focussing options (excellent tracking and its peaking actually works accurately all the time). In the context of a pocket sized travel camera the RX100M3 more than makes up for those shortcomings however.