Some might be wondering about these terms on some files.
Here's how I usually handle these.
The goal is to be clear this isn't the same original scan being uploaded twice - that people might want to grab this new alternative version for their collections.
When completely new scans are made from a new source comic it's a 'diff ver'. 'Upgrades' would include jpgs from the first version with perhaps a better cover or missing pages added to improve on the first version. 'Rescan' files usually means a rescan of the same original comic but at a higher resolution. Freddyfly's rescans fall under this.
Hope that helps,