So for a beginner actually it should be samantha first or vipassana then samantha. While I was googling samatha and vipasanna, there was this one article claiming Myanmese teachers having no difficulty teaching samatha initially then vipassana later stages. However, when they started with Western students, it was very difficult as the Western due to there cultural back ground were mentally more active.
Let me elaborate, often our mind is compared to as monkey or elephant mind, sometimes visually presented as monkey sitting on elephant. This represents our state of unrestrained/ untrained mind.
It could be like a monkey running all directions and the more you try to control or restrain it, the more agitated it becomes.
The opposite is the elephant mind, toporific or slothful mind. Try to leash and move an unwilling elephant! You can't! It does what it want but pass around.
Yes, we can be predominantly agitative or slothful, but really we can be a mixture of both. Nevertheless, we must start somewhere. For years, I practiced calm abiding or samantha only to find myself becoming more agitative and wishing to escape the practice. Occasionally, I might have nailed it, but couldn't maintain a constant practice,I did not actually find the right formula. Needless to say, I was not particularly enthusiastic and could not follow through.
Only the other hand, if you are slothful or dreamy mind, probably vipassana will strain your mind lulling you to drift off to sleep. Generally, I am mentally active most of the time, however, I have a certain period where I was physically active and when it comes to meditation, calm abiding comes more easily without having to control the "monkey" mind.
Right effort; in this context putting right application on a particular mind state. We are dealing with a gross state initially and therefore deal with it appropriately.
So as personal conditions change, so our daily initial mindset change. Generally I believe if you find yourself mentally active until the last minute to sleep, you should start with with vipassana practice. Simply watch your thoughts running around without restraining them;initially. Pay attention to gross reaction or emotion.As time goes by, your scattered thoughts become more collected, you will start to sense the patterns and emotional triggers your thoughts give and vice versa, you may start to understand your personality, your karmic imprint so far. You may not have full absorption initially, but at least you have lasted so far, and will continue from gross emotions to conceptual or judgemental thoughts without emotions. Your mental control has actually improved.
For people who are not so mentally agitated, calm abiding is much easier as the mind settles much faster. But why then, the need to do "awareness of" training? Well simply it is an investigation tool we need acquire insight to "Self" or "No Self". Being with better collectedness allows you to deal with more subtle thoughts process. The danger is not wanting to investigate.
Each time you will find you experienced in line with Buddhist teachings.
Also, these two starting approaches also works with Mantrayana. It doesn't change the way our mind essentially works, if fact, it provides a period of stability in both familiarity and regularity allowing the rising and non arising in our minds. Same mind, same chanting different mind thoughts at different times. Notice I did not emphasize on posture or breathing, just get comfortable, leaning against the wall if you want to. Past your first hurdle first. Correct those later.
The point I am trying to put by putting the right effort vipassana can lead to samatha and vice versa, just what gives a better grasp initially. Especially for mentally more active people who might have a develop a phobia by starting at the wrong end. Reach to a level of comfortable habit sitting of longer and longer periods. Our mind will eventually collect, those periods of non calm abiding is not as unproductive as you think. It will create a basis and foundation. Each achievement, either calm abiding or awareness reinforces each other. One rung of the ladder before the other. So you can either face your monkey or you elephant first but ultimately you can rein and ride both.