I also have a suspicion that the initial default image presented to you when you open a file does influence how you process the image and what kind of a result you end up getting and that may well explain some of why I've never really been happy with Olympus Viewer because I tend to like a different kind of result to the Olympus JPEG modes. That's a matter of personal preference in a number of areas including interface and working styles. For some reason I never really felt happy with Olympus Viewer but many people swear by it. I think it also has a longer and steeper learning curve and that isn't what a lot of people want but the longer I use Lightroom and the more I learn, the easier I find it to get the results I want. In my view Lightroom gives you a lot more control than Olympus Viewer. What counts is how much control the program gives you over the finished result and how easy you find it to get the kind of result you like as a finished product. Comparing those initial images with default processing tells you nothing about how good or bad an application is at RAW conversion.
Every RAW conversion program has a different idea on what kind of processing should be applied before showing you an image that you can use as a starting point. That's because no RAW conversion program shows you the RAW image because there is no RAW image, just sensor data that needs to get a fair amount of processing before it starts to look something like what you saw when you took the photo. What you will find if you open the same RAW file in both Olympus Viewer and in Lightroom using their default settings is that the images you see in each are going to different, perhaps even very different. Adobe's default mode, Adobe Standard, gets panned regularly as not delivering the kind of colours people want but I actually think it delivers reasonably accurate colours and while I've tried the other Adobe profiles and the Huelight profiles I have always ended up back with Adobe Standard as my default profile and starting point.
Lightroom offers a number of camera profiles that are intended to give a result something like the camera modes but I haven't seen anyone say that Adobe really nailed it. Other RAW converters including Lightroom don't have access to that proprietary information. If what you want is to be able to get results like those out of camera JPEGs with the option of a lot more control over the result, then Olympus Viewer is going to be the easiest, quickest, and most reliable route to that result. What Olympus Viewer has going for it is that Olympus know what the "secret sauce" of their naturall/muted/portrait/vivid/dramatic and other modes are and Olympus Viewer is therefore the only RAW converter that lets you get exactly what each of those modes would give you as an out of camera JPEG, at least without you having to put in a fair amount of work trying to duplicate the out of camera JPEG result. But I really like its basic RAW conversion. OV3 is slow (very slow on some computers), rather clunky, has bugs, and does not offer the most advanced processing algorithms. Then I do additional processing with other programs that have more advanced sharpening and local-contrast algorithms, such as Image Analyzer and RawTherapee. I start RAW processing with OV3 to obtain the color accuracy and lower noise. I have tried several times to identify a sharpness hit from this hidden noise reduction, but so far I haven't been able to spot any. I think the program is doing some things it's not telling us about. When I compare OV3 and RawTherapee on noisy images, OV3 always yields markedly lower noise, especially color blotching, even when I have disabled all processing in OV3. I do believe colors from OV3 RAW and camera-generated JPG are the same, however. I started to list them, but there were too many.
Olympus Viewer 3 provides many options and adjustments not available in the control screens of my E-PL2.