A Simple Modification Before you can effectively smoke in most of these style grills you need something to block the direct heat. Big Green Egg calls this a plate setter and they sell for about $50USD. Other Kamado makers have similar products. This indirect baffle blocks the radiant heat of the burning charcoal and let you grill indirectly. Adjust the vents to hold a low and slow temperature and you have a smoker worthy of use in barbecue competitions.
Advantages Because Kamado grills are capable of hitting temperatures over 750 degrees F (400 degrees C) they are excellent grills. Add to this the low and slow capabilities and you have the most versatile outdoor cooker on the market. Kamado grills tend to be very durable (unless you drop them) and are rather attractive.
Disadvantages When compared with other charcoal grills, Kamado grills are considerably more expensive. Of course, when balanced with the advantages they can be worth the investment if you are a heavy user. The other disadvantage can be the size. While prefect for backyard barbecue, the space limitations of most Kamado grills doesn't give you the area to do a lot of barbecue, so while you will see these at barbecue competitions, the competitors typically bring several.
Metal Alternative There is a metal version of the Kamado grill on the market called the Big Steel Keg (as opposed to Big Green Egg). This version uses high temperature insulation sandwiched between an inner and outer metal skin. The Big Steel Keg actually has better insulation than the ceramics and a considerably better seal between the lid and the body than most of its competitors. It is, however, metal and needs care to prevent rusting, and is an 18.5 inch grill, like many of the other Kamado grills.
Bottom Line If you want a single unit that gives both high temperature grilling and low and slow barbecue capabilities then the Kamado grill is the best bet. There are a number of manufacturers on the market. It is best to purchase one of these from a reputable and specialized dealer who can provide assembly and delivery as well as support and accessories.