Although the death mechanism in strangulation is the same as in hanging (blocking the oxygenated blood supply to the brain), here you depend on how tightly you can tie the ligature to exert pressure and compress the arteries. In hanging, however, you use your suspended weight to achieve this.
Just because it's a little more difficult doesn't mean it's ineffective.
In my opinion, it takes even more determination to use this method, and it may be a bit more 'extreme'.
Comparing it again to hanging, once you step into the void, your weight and gravity will do their work, closing the ligature knot and compressing the neck. In strangulation, it's all up to you.
There are several cases of strangulation (including forensic photos) in these books (may be a useful reading):
Forensic pathology of asphyxial deaths by Dr. Sudhir K. Gupta
Printed book page n° 103, Pdf page n° 118
Printed book page n° 117, Pdf page n° 132
Asphyxiation, suffocation, and neck pressure deaths by Burkhard Madea
Printed book page n° 180, Pdf page n° 193
Printed book page n° 70, Pdf page n° 83
Autoerotic deaths: practical forensic and investigative perspectives by Anny Sauvageau and Vernon J. Geberth
Printed book page n° 123, Pdf page n° 140