Sudarshan kriya and sahaj samadhi meditation are two total different things. Sudarshan kriya is a typical pattern of breathing. In patanjali yogsusutra, it is explained how we gain control over our mind through braking of rhythm of our breath. Su means sundar (beautiful) and darshan means purifying action. Thus Sudarshan kriya gives you knowledge who you really are. It brings you in the present moment and relieves you from the stresses. This you can experience in the entry course of Art of Living (called as Happiness Program) You have too many responsibilities (say at office or at home or in society), you have limited time for performing these responsibilities with your certain energy level. You can not reduce responsibilities. You can not even increase the time (beyond 24 hours per day) So only option.
remains with you is to increase your energy level. Sudarshan Kriya gives you this increased energy level if you do it regularly. There are many more advantages of this.
Now, coming to Sahaj Samadhi Meditation, as the name suggests, it is a meditation. As is a general belief, meditation means concentration of mind. But in fact, it is just opposite. It is de-concentration. Concentration of mind is the effect of meditation. During any meditation, you have to remember just 3 things.
For the next 20 minutes,
1) I am nothing
2) I want nothing
3) I do nothing
In Sahaj Samadhi meditation, you get one (personal) mantra for using during meditation. In meditations, thoughts keep coming to mind, but for a few moments, thoughts stop coming. That is during deep meditation. It is a rest for our mind. Just a few minutes of meditation is equivalent to few hours of sleep. That is the value of meditation.