AS a former Kamado owner and current summit owner I will say the summit is the best of all worlds. I have been very critical of a lot of Weber's new products and innovations but this is not one of them.
when I had my kamado, I used it for 1 thing and it was REALLY good at it. smoking, I never fired it up for grilling. Why, it was kinda of a pain to do for a simple grilling session, doing indirect was a project if I wanted to do it.
The summit, with the ability to move the charcoal grate from lower to upper allows for the kamado style smoking and the kettle style grilling. The gas assist in the summit is rather worthless as it is so low in the kettle if you are grilling you would like your coals and need to figure out how to get that hot grate to the upper rack.
My only know on the summit was price, they over priced it initially, the Kamado 6 or whatever the new version is, is more in line with what the initial summit should have been.
If I could only have 1 grill, it would be the summit charcoal grill.