Do not get too caught up in the Oval shape of a Primo, especially if you are looking at a XL BGE. I have an XL BGE, I can easily fit a brisket, racks of ribs, etc, with no meat hanging over/exposed to direct fire.
You can easily set up the egg for direct/indirect cooking with tools from the Ceramic Grill Store.
I went with the Egg due to more support with forums, 3rd party products and just overall reputation.
I haven't see a KJ up close and personal, but I've seem Primos and Eggs, and both are quality.