The Atlanta Blade Show is much bigger and more varied. It has a bigger draw from Europe (based on my limited attendance).
Las Vegas will not have as many East Coast or central US knifemakers but, will have a better draw from the western US and the far East (Japan). Because the show is smaller, it has a more intimate feeling and it is easier to speak with knife makers at length (they aren't constantly being hounded by throngs of people).
In general, Las Vegas has fewer tables, no factory knives and, a more intimate feel. Atlanta is a much larger show, you will see screen names in person and, it will appeal to a more mass market audience with collector displays and gun show type knife dealers selling production stuff.
There also is the obvious non-knife related draw of the Las Vegas night life (shows and gambling) versus the Atlanta night life (I really like that part of the country but, big city Atlanta night life just ain't my cup of tea).