Here's something I find baffling.
The differences between 1.jpg and 2.jpg is that the latter is stripped of EXIF data and the file size is obviously smaller.
Useful to know if you want to keep the EXIF data with the .jpg (or not). Is there a simple explanation for this?
"4. Export for Web discards the EXIF data."
'Fraid not. I thought that was the point of it - to strip out the metadata to make the file smaller and hence more suitable for the web. Whatever it does, it doesn't do that!