ronniemac wrote:
I traded in my K-S2 for a K-70, and know it to be a good decision for me for the following reasons:
1. Sensor is far less prone to noise, especially in low light
2. Sensor has higher pixel count, therefore capable of higher resolution photos which can matter when cropping.
3. Much improved grip - crucial for me.
4. Pixel shift is available for static subjects and noticeably improved colour, further reduced noise, and clarity.
5. Astro tracing feature good for shooting start when coupled with O-GPS
6. Better for video.

Other differences are minor, e.g. f.p.s., weight and size are very minor.

The K-70, which is in current production, superseded the K-S2, so is more readily available, but I would expect the former is slightly more expensive. Upgrading from a K-S1 to either would be a wise decision if your interest is in landscape photography because they are weather sealed.

Both K-S1 and K-S2 are remarkably good value for money, but from my experience using them both, the K-70 is without question the better camera.

JAK wrote:
Exactly. I often take my K-S1 out rather than the K-1 as it is one of the lightest DSLRs out there and lighter than some mirrorless offerings. I have to ask the OP, what do the K-S2 and K-70 offer for the task that can't be achieved with a K-S1 ? I really can't believe changing would make any significant difference to the results you get from the KS-1.
If spare photo funds are available, maybe look to spend them on faster or useful focal length lens. While the 18-55 is not bad, there are better alternatives. A faster lens would allow more available light indoor shots without the need for flash. A wider lens might be useful for getting group shots in confined spaces. A longer focal length lens to get more candid photos from a distance.
I'd certainly think it through again.
By the way, welcome to the forum!

Nigelk wrote:
I have the K-S2 and am very happy with it.
To be honest I'd recommend getting the one you can get the best deal on. Either will be great for your needs from the sounds of your brief.

stub wrote:
What is the problem with the KS-1. This should be fully capable of the task in mind...