There may be many techniques that attempt to reach or develop the same thing. Each one is appropriate for someone, somewhere. So I wouldn't claim TM is the best or conscious breathing is. There are many other factors other than the method itself that determine the success of the practice or spiritual progress in life. Mantra meditation (as in TM) has its a wonderful effects but also limitations. One may remain closed to certain abilities and gifts that are ready to come through, and some poeple just don't know how to handle their mantras without straining. Apart from that, you need to be very well off financially to be able to afford TM. On the other hand, conscious breathing is just as effective, and it leaves room for other things to unfold. Besides, it is free.
You can use any other chants you feel attracted to, if you want. We humans have so much lived by the rules that we don't much trust our own feelings. Rules don't make us any safer, in fact, they instil in us the fear of what comes after we break them. So many of us remain imprisoned by the idea that we need to be guided by others, by books, codes of ethics, etc. because we are not competent or good enough to know what is best for us. But it is time to break free of all these self-imposed or accepted limitations. So let your heart speak for itself and honor everything you come into touch with. Everything has value, good and bad, right and wrong, dark and light.
With kind regards,