Originally posted by cartesio but I would like to be sure I am going to get something significantly better than what I already have.
"Significant' is a rather subjective concept. I do happen to find the KP "significantly" better than my E-M5ii, not just for dynamic range, but for the ISO and Pentax image processing. In fact, since acquiring the KP a two and a half years ago, I haven't used my m43 stuff all that often. Prior to the KP, I used m43 quite a bit, mostly for the vastly superior image stabilization of the E-M5 (vastly superior to my K-5iis). But the five axis stabilization of the KP makes it, for me, useable as a low ISO hand-held camera. And the images from the KP strike me as being just better. Not necessarily sharper, but better color, more life-like rendering, greater sense of depth.
But all this, of course, is "subjective." When I look at images on Flickr, most of what I see could easily have taken with m43 gear. The main advantage of larger sensor cameras (other than ease of attaining narrow depth of field) is that images from those cameras are more resilient when it comes to post processing. But a vast number of photographers out there seem allergic to PP, and if you're not going to PP your images, m43 may be all you'll ever need. Even in terms of so-called "low-light" photography (which I translate as photography in low light sans tripod or flash), with a fast 1.8 prime and an m43 camera with state of the art stabilization, m43 may be just as good as an APS-C camera like the KP. And that's particularly true if you're not going to bother to post process the images. With low light images, I like to have five or six stops of dynamic range to work with in post. But if you're not post-processing dynamic range considerations are often irrelevant.