Comment by rjknight

One of the neat properties of base58 (and, strictly speaking, of base62 as well) is that it does not contain any characters that require special encoding to be used in either a URL or a filename. Nor does it contain any characters that are considered to be "word-breaking" by most user interfaces, so you can do things like double-click on a base58 string to select the entire string. Base64 has none of the above properties, while being only very slightly more efficient.