When considering an integrated headset, you need to think of it as part of a system—a bicycle frame, fork and bearing system. The goal of this system is to get rid of the headset cup that characterized headset design up until the creation of the integrated headset.
The question you might ask is what, then, has actually been “integrated” into the headtube by recourse to an integrated headset? Well, instead of being located inside pressed-in cups, the bearings now rest inside the frame instead. It seems like a lot of work, fuss and bother just to do away with two 12 gram headset cups from the front of your bike. An integrated headset gives a bike a nicer, smoother, more streamlined looking front end though.
An important advantage in using an integrated headset is that you do not have to use any special tools. To install a standard or internal headset into the head tube, you’ll need a headset press . This consists of a rod with a handle at one end. The rod threads through the head tube with the lower cup is seated on the lower end. The upper cup is seated on top with the handles rotated just above. As the tension increases, the cups are progressively pressed into the upper and lower edges of the head tube. The tool is expensive and not all that convenient to use, to say the least. Moreover, you will need a headset cup remover tool and a hammer to tap out the cups come time to replace the system. Use a screwdriver by all means. However you will likely damage both the components being removed (maybe no big deal) and your headtube (definitely a big deal). All it takes is a slip of the screwdriver.
By contrast, the only tools you need to install or replace your integrated headset is an allen key/hex wrench (normally 5mm) to loosen the tensioner bolt and remove the top cap. Even if the bearings are firmly seated in the headtube, it won’t take long to remove them just using your fingers, although a bearing cup removal tool here is invaluable for bearings that stubbornly refuse to dislodge.
There is some debate about the degree of increased performance we gain by using the integrated headset design. Many feel that there is a reduction in performance and in the lifetime of this type of headset unit. The argument is that the bearing is not securely attached to the frame. The bearing thus sort of ‘floats’ freely which means movement, and where you have movement you have increased wear and tear—in short it’s not good for the frame and the longevity of the headset is reduced.
Another bone of contention is that each manufacturer comes up with slightly different designs and thus different spec. Without effective standardization up to the present moment what we have are a wide variety of bearing types and sizes. Additionally some of these have been discontinued with no replacement options. Frame builders and bearing makers are also not all working from the same drawings. That makes it a bit harder when sourcing replacement units or parts for those units.
A counter argument to this is that the movement or play that we are talking about here is not really significant. If an integrated headset is properly installed, then there may be a fraction fraction of a millimeter of play, which results in some minute wallowing of the head tube bore. There will be considerably more movement if these headsets are not installed and adjusted correctly. It is fair to say that for most riders and their bikes, the fractional wear that occurs in a properly adjusted headset is not an issue. Something else on the frame will go long before the bore is affected to the point where you can declare a frame compromised. The fact is that any headset that is not adjusted properly can damage a headset. This is not a case of the inherent weaknesses of the integrated headset vs all the rest.