Vedas are not only just some chants or some type of books, they are the fundamental building blocks of this universe itself. Every part of universe is composed of some vibrating Veda mantras. The particles contain abundance of RigVeda (Ayam Lokoh RigVeda), the space consists of abundance of YajurVeda (Antarikshyam vai YajurVeda), the photons or bright particles/light contain abundance of SamaVeda
Lord in Bhagvad Gita tells he is SamaVeda among the Vedas, in the Vibhuti chapter where all the things told are such which shows shining nature of all. Now, we have to find how SamaVeda is shining than other Vedas. For this we have to think of what are those places which contains abundance of Saman? For this we have to look upon pramanas of Rishis from Vedas.
Samans are very sukshma and we can't observe them directly with our eyes. But we can consider those particles which contain abundance of Saman as Saman themselves for understanding. And we get that the most appropriate representative of Saman is light (photons). This is made clear in Shatapatha Brahmana:
From above verse we can have faint understanding of Samans. We can consider them as rays of light ( to say in the term of modern science - Photons). Due to this everything which has brightness in this world contains Samans:
And most importantly whatever interactions are taking place in this universe is only possible because of Saman (Modern physics also tell that for any interaction to occur mediator particles- photons are needed).
From above all quotations it is clear why Lord told that he is SamaVeda among Vedas. But this doesn't mean that SamaVeda is the only superior and other Vedas are of no use. Each Veda and each mantra of Veda and each syllable of mantra is very important. Just like light/photonsArchi are formed mainly from Samans similarly, Space/ Antariksha is formed from Yajush and molecules/ Prithivi tatva are mainly formed from Rik.