In the name of transparency I actually work at King building Cielo bike frames so maybe my opinion is biased. The advantages for my build are lower stack height, larger headtube diameter and of course it's a Chris King headset. We do build a steel production bike with them that you can check out here http://cielo.chrisking.com/bikes/mountain-bike-details/ The bike I built where I turned my own head tube was a "Bakfiets" cargo bike where the large head tube was a huge plus because my main tube was a 2" and I would have had to do pretty drastic squeeze to miter to a 36-37mm head tube. I'll try and get a few pictures of my cargo bike up. The only disadvantage that comes to mind is the need for another sized reamer and facer set to prep the head tube. I had pretty easy access to one but I honestly don't know how prevalent they are out there. Bike shops selling the InSet should have them.