A first panorama (1MB) follows:
In my opinion, it is crisp and clear.
Now there is a second panorama to follow:
It is quite "blurry" or "muddy" all around. The details are overwhelmed by sort of artifacts.
Some different assumptions could be suggested as follows:
1) The lens that was used to shoot the images for the first panorama is sharp. Wehereas the second panorama was made from a lens that makes for some reason very blurry images
2) The images that were shot for the second panorama are from a "shaky" camera on a flexible tripod, or with a long exposure or whatever reason to get "blurred" images. The images from the first panorama were shot with much more care in order to get crisp photographs.
3) The sources images used to stitch the second panorama were artificially blurred with a Graphic Editing Software whereas the images for the first panorama were a contrario kept as sharp as originally possible.
4) Some figures in the Images Setting Parameters (PTGui) for the second panorama were tweaked a little bit off from the best (calibrated, optimized and used for the first panorama) in order to produce this "blurry" effect after blending.
5) On the output equirectangular image of the 2nd panorama a blur filter was applied mainly on the center horizontal part (the top and bottom seem quite sharper).
The answer to the question is here.