Boss Katana heads

Thinking about getting one of these but not really sure what the differences are between the Katana Air and the Katana Head. Apart from one being wireless, of course.
Also, I can get a used mark 1 Katana 100 head for under £200. How much of a difference is there between the mark 1 and mark 2 to justify paying almost £400 for the new one. Any thoughts from Katana head users.
Also, I can get a used mark 1 Katana 100 head for under £200. How much of a difference is there between the mark 1 and mark 2 to justify paying almost £400 for the new one. Any thoughts from Katana head users.