I have a large BGE and a buddy of mine has a kamdo.
1) Performance is roughly the same
Plus to the BGE. Multiple sizes and countless accessories allow you to cook more items
The BGE has 5 different sizes including the giant version released last year. The Kamado is about the same size as the Large BGE
Both are very durable. The BGE firebox is prone to cracking but it won't affect the cooking and is easy replace under warranty. You should always keep them covered but the Kamado finish seems more prone to damage.
No idea on the Kamado but my experience with the BGE has been first rate. My fire box cracked after a year and they simply mailed me a new one. I still use the cracked one, since it doesn't affect anything and I have the new one in a box as a backup.
My BGE is almost 4 years old and still looks brand new. I had to replace the felt gasket last year due to a screwup by me.
This post was edited on 2/7 at 6:24 pm