It depends on the data. Base64 adds ~33% overhead, while NUMBASE can be encoded into one large number at once and compressed with Huffman or other algorithms. For some data types this results in fewer extra characters.
Base64 is great and widely used. I just wanted to experiment with a numeric-only representation. NUMBASE encodes everything into a single large number, which can make certain compression schemes like Huffman more efficient and opens up new ways to store or transmit data.