Why is it said that the Mahimnah Stotram is the best prayer?

It is the best prayer as you can see the title itself. The word ‘Mahimnah’ means that it is the prayer of the miracle. Miracle means the unimaginable event indicating the unimaginable God. It means that you are praising the actual-original-absolute-unimaginable God through the medium called Shiva. Shiva is the energetic form possessed by the unimaginable God. Here, Shiva is recognized as the unimaginable God identified with the energetic form called Shiva. The last verse of this prayer denotes this meaning. The last verse is “Tava tattvam na jaanaami kedrushosi Maheshwara, yadrushosi mahaabhaaga tadrushaaya namo namah”. The meaning of this verse is “I do not know the essence of Yourself, called Shiva. Whatever be Your essence, I salute to that essence identified with You as Shiva”. If you analyze this meaning, it clearly establishes the unimaginable God. One cannot know the unimaginable God, who is the essence of Shiva. Such essence, the unimaginable God, has charged the energetic form called Shiva. Due to this charging, the essence (unimaginable God) is identified with Shiva. Therefore, Shiva, though visible energetic form, has become the unimaginable God. Therefore, visible Shiva became the unimaginable. The salutation is rendered to such unimaginable Shiva, who appears as the visible energetic form called as Shiva. This prayer has the knowledge of the unimaginable God existing in the energetic form called Shiva.

Similarly, in the human incarnation like Krishna, you must have the knowledge of the unimaginable God in that human form. The value of the human form is only that unimaginable God. Since you cannot isolate the unimaginable God from Shiva or Krishna, you have to treat Shiva or Krishna as the very unimaginable God. The current is invisible to the naked eyes. The current is flowing in the visible copper wire. Since the current is identified with the visible copper wire, you have to treat the copper wire as the invisible current. This means that the visible wire becomes invisible simultaneously. Due to this last verse indicating the unimaginable God, who is indicated by the title itself, this prayer is considered to be the best and topmost. Hence, it is said ‘Mahimno naaparaa stutih’, which means that there can be no prayer equal to this Mahimnah Stotra.