There is a difference. The recently announced trade edition has a blurb by King printed on the top of the front board. There will likely be a price printed somewhere on the back cover as well as a bar code. The 150 or so copies distributed at the SDCC had no blurb or bar code.
The one currently being sold by CD and amazon (and others) is the later trade edition. Time will tell what the future value of each edition will be but "first is first" and the books distributed at SDCC are definitely earlier.