BTG,
In a previous job I oversaw the sales of both BGE and KJ. As far as cooking they're virtually the same. I liked BGE's customer service better from a retail perspective but if I had to choose one I would get the KJ, the hinge system and assembly is better.
As packgrad said, the big thing with a ceramic cooker is the versatility. Both of these brands use charcoal very efficiently(side note, ONLY use natural lump coal, I recommend the FOGO brand if you can find it). There have been times that I have smoked a boston butt overnight in my BGE XL at 225 and had plenty of enough coal left to run it up to 600+ that night to sear a steak. Typical 400ish degree cooks you can get 3 or 4 at least in my experience(filling up the basket)
As far as lighting it, I had one of the bison lighters that you charge and has the fan built in. It was nice but the absolute way to go for lighting charcoal is the JJ George lighter. Get one of those and a six pack of the coleman tanks at Lowe's and you will thank me later. I can have my Egg/KJ going hot in no time. Plus it's really fun to use
Other accessories i use are the Kick Ash Basket and the Smokeware top cap. And my Grill Grates, of course.