They both use the same size sensor but Sony tries to squeeze out more pixels (18MP).
That means the pixels are smaller and that means they produce less light per pixel.
Raising the ISO to make up for the loss of light means more noise,
For low light situations the Panasonic 12MP is the better choice.
...
Short story: If I'm interested in image quality straight out of the camera, speed in terms of auto focusing and shot to shot, which should I choose?
Sony HX20V for $180
Panasonic ZS50/TZ70 for $360ish
Long story:
I've had an HX20V for several years and really enjoyed it. During a recent vacation a family member got some sand in it, which would require a $300 repair to fix. The family member has therefore offered $300 to either fix my old one or apply toward a new camera.
The thing(s) I really don't want to lose are the speed of the HX20 in a variety of settings (snaps as well as auto focusing) and I don't want less than 20x zoom while remaining in a relatively compact size. I've been quite happy with the image quality. I've done prints up to 11x15, but I don't pixel peep. I also like my picts to come out well straight from the camera, no post-processing for me (so RAW doesn't matter to me). Also, I want the pictures to come out well in regular auto mode, without having to tinker with various settings. (I do tinker at times, but I want it to be optional and not mandatory to get really good images).
I'm a bit intrigued with Wifi, but it's not crucial for me. I don't care about GPS. Viewfinder is nice, but not necessary. Getting an extra 10x zoom would be nice, but only if I'm not sacrificing quality in the first 20x. An articulated screen (like the Sony HX90V or the Nikon S9900) would be really nice, but those two have other issues which remove them from consideration. I haven't been able to hold the ZS50, but the ZS40 felt a little thin gripwise for me, so based on my readings the ZS50 should probably work well.
So is newer better? Is it worth the price difference?

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