Despite what Lawson English says, all meditation is either Samatha or Vipassana. I will not debate the merits of one form of Samatha (like TM) over another one but will give the perspective of Buddhism.

Samatha and vipassana are like the 2 wings of a bird. The bird cannot fly if it does not develop both.

Then comes the question of whether one should study one first, or the other, or both at the same time. The historical Buddha said that all 3 options are valid ones. So it becomes a matter of taste, really, whether you start with Samatha, vipassana, or both at the same time.

One other thing you should note, is that although the focus of a particular meditation is either Samatha or Vipassana, you will always develop both at the same time.

By this, I mean that if you take the typical Samatha meditation of following the breath, you will also end up with a lot of insights into the workings of the mind. But that is not the main focus of the exercise.

Reversely, if you take a Vipassana practice like modern-day mindfulness, you will need to develop some degree of concentration (Samatha) or you will get nowhere.

So, choose the one that appeals the most to you, and start there. Doing what you like is often much better than doing the ‘best meditation’ that you dislike and will not follow through.

On the note of ‘best meditation, this really does not exist. If you ask 10 different people from 10 different traditions, you will get 10 different answers. I am in many groups and follow many forums, but I only stay in those that are open enough to acknowledge that there are many equivalent methods and that the best one is the one that suits you.