Image Display Query
Using Jamroom
Not a fair comparison. In your screenshot both images look the same size, but they're not. The one on your site is 1280px. Its been reduced to that size so that it loads faster over the web.
The full size image is on this url:
https://pmp-art.com/gallery/image/gallery_image/215280/original
The full size image is 4288px wide.
So the answer to your question is the bigger image looks better because it has more detail to it. When an image is reduced in size it looses detail.
--edit--
If the user was to compress the file to 1280px before uploading to your site, then compare what they had with what was uploaded they would look the same.
--edit edit--
Also the "Convert to JPG" could also have something to do with it, its a setting at:
ACP -> CORE -> IMAGE SUPPORT -> GLOBAL CONFIG -> GENERAL SETTINGS -> CONVERT TO JPG
When using this, to save size, the image is reduced to 85% of its full quality.
updated by @michael: 07/23/17 07:26:48PM