I own a large and a small. I've cooked next to XL's at our Eggfest, and 2 buddies have them. The headroom is shorter, but I think they have changed the fire ring height to give you more room. Everyone does say it's easy to get the pit temp higher than what you want, but once they practice with vent control it's no big deal.... just different than a large is.
The XL is really big compared to a large. Tom at ceramicgrillstore.com has a lump reducing ring to use if you are doing a smaller cook in the XL Egg.
Also FYI...., Primo has just come out with a special Jack Daniels XL Oval edition, and is planning a Large Oval (which will be in-between the Oval Jr., and the XL Oval.)