Comment by wtbob

The base64 & hex stuff is only used for the advanced, human-readable bits; on the wire it's just straight length-encoding and byte strings.

I'd say that bencode's advantage is a built-in standard for integer encoding (with canonical S-expressions one must decide between ASCII decimals or little/big-endian bit strings), and a clearer standard for a dictionary/map/hash (a canonical S-expression would probably use an alist-like structure like (map (foo bar) (baz quux)), but one could also go with (map foo bar baz quux), (map (foo bar baz quux)) or some other encoding.