Which meditation is better to do: Awareness meditation(such as:Vipasana) or concentration meditation (such as: Tratak)?
Vipassana meditation is basically used not to concentrate or focus you just sit and observe you sensation. yes when you are sitting and you feel hot, cold, itch, pain, thoughts, anger, hatred, breathing everything inside your body sensation.
So what happens is sometimes you feel very good and enjoy meditation there comes the problem you are supposed to observe this enjoyment as well, i mean do not just get flown away by good or bad feelings.
You should do this in group sitting, that may give you more confidence.
See there are 108 ways of meditation given by Lord Shiva, you can pick any of them all leads to the same place, as Swami Vishwananda said in comments "The goal of meditation is freedom FROM the senses; not freedom of the senses"
I would suggest you can try different meditation techniques from different gurus and pick one which makes you more confident but remember in all meditation you are not supposed to get attach to a feeling just sit observe and get up, because you may get stuck at a point for your entire life.
So in essence of this answer if it does not matter which one you pick, it is just that how bad you want it, also how you eat is also very important in Yoga.