What is the difference between reciting "Namo Amitabha Buddha" and reciting "Amitabha Buddha"?

Namo means taking refuge, expressing sincere reliance and submission; Amitābha is the name of the Buddha, the principal deity. Reciting the Buddha's name is in order to resonate with the Buddha, to attune oneself to the Buddha, to seek the Buddha's blessing, His outstretched hand to draw one out and save one. The two methods of reciting the Buddha's name are inherently no different, but with two extra characters, the mind's recitation winds about; it is not as direct as reciting "Amitābha," the mind is simpler, and it is easier to attain samādhi.

Reciting the Buddha's name is not purely for the sake of reciting the Buddha's name, but rather to gather the mind, to sincerely take refuge in Amitābha, and to attain the samādhi of Buddha recollection (buddhānusmṛti). Only within the samādhi of Buddha recollection can one resonate with Amitābha and attune oneself to Amitābha, and only then is there assurance of rebirth. Therefore, in reciting the Buddha's name one should also try one's best to settle the mind; the mind must be single-pointed. When reciting the Buddha's name, the Buddha should be present in the mind, reciting with a reverent heart. In order to gather the mind and attain concentration, the voice when reciting the Buddha's name should not be too raised, for this exhausts the breath and the mind easily becomes scattered and hard to collect. With a lower voice, more gathered together, the breath is consolidated, the mind and spirit are at peace, the mind is focused without stray thoughts, and it is easy to attain concentration, attain the samādhi of Buddha recollection, and receive the Buddha's blessing.

In order to recite the Buddha with the mind and attain the samādhi of Buddha recollection, one may try reciting in this way: slowly sound out the syllable "A," drawing out the sound of "A" long, without reciting "mituofo" (Amitābha), while at the same time holding Amitābha, the principal deity, in the mind. The syllable "A" is manifest outwardly, while the three characters "A-mi-tuo-fo" are hidden at the bottom of the heart—one syllable standing in for the whole Buddha. With no stray thoughts in the mind, all is the Buddha; reciting in this way, it is easy to attain samādhi.