I don't have the 14-140 so I cannot really comment on that lens. I do have the 45-200 and use that with the Olympus 14-42 and Panasonic 20mm lenses.
I am not surprised that you cannot tell the differences in image quality between the 14-140 and the 45-200. Such differences would be most minor. I am not surprised that the 45-200 has better corner sharpness compared to a 10x zoom. Such long zooms are very much about finding the right balance in compromise and something has to give.
I do find that the 45-200 is a bit of a pain and not wide enough quite often which leads to the inconvenience of having to change lenses. In most situations that isn't a big problem but if you are out in the field in rotten conditions (wind, rain etc), or don't have much time to change over, the 14-140 would be the way to go.
The other things that I don't particularly care for in the 45-200 is the close focus distance. I find it just a bit too long, 0.6m or so would be much better.
I also find it misses focus from time to time and is particularly difficult to manual focus. The missing focus is probably due to the Olympus E-P1 which has far too large an AF focus spot. The difficulty in MF comes down to the long focal lenght and slow aperture. On the other hand, the 14-140 is even slower at the same focal lenghts.
I am waiting for Olympus to release their 14-150 and see what the price and performance of that is like. I would expect it to be marginally cheaper than the Pansonic but not necessarily a better lens. The differences would be most minor. I may well go for either the 14-140 or 14-150 as a single lens holiday kit and when combined with the 20mm will do just abuot everything I want.
I don't know. It's a hard choice. I would have thought the 45-200 would have been the longest zoom I would ever need having only ever briefly had a 200 lens on a full-frame camera. I find myself now using an old Olympus OM 200mm lens with a 2x teleconverter and still wanting more.
If I were starting from scratch today and had the same knowledge, I would go for the 14-140, 20mm and be looking at adding a longer and shorter zoom later (e.g. 9-18 and 100-300 or thereabouts).