...did you reach any interesting conclusion comparing the Pentax with the Nikon?
I suppose that depends on how you define "interesting." I found it interesting that neither the Nikon nor the Pentax impressed me nearly as much as I had anticipated/hoped they would.
Don't get me wrong, the Nikon is a
fantastic little glass but, it
is little - with all the basic problems this inherently imposes, i.e. dim at the upper magnifications, lower resolving power, etc. It has after all, a 50mm objective lens and the laws of physics still apply. It would be
wonderful to use during the day when it's bright or if you were travelling or backpacking and needed to keep weight, size to a minimum but, I can't imagine it being acceptable for an "only" or "primary" spotting scope. It is definately a specialty glass. Even so, I really want one (or something like it.)
The Pentax, with its higher 65mm objective lens is obviously brighter and can resolve detail better but, at the expense of greater weight and bulk. It would be clearly the better choice as a primary scope - but it still is a compromise in optical performance from bigger 80mm scopes.
Personally, I don't find the 60-65mm spotting scopes to be very acceptable. They compromise too much from all areas doing lots of things "O.K." but doing nothing great. This is why I now have a good 80mm scope for general use and am looking for the best value in a 50mm scope for travel and backpacking.