Base64 encoding or bin2hex random string

When converting "random bytes" to a string, is there any difference as to whether I should use base64_encode or bin2hex?

$bytes = openssl_random_pseudo_bytes(32); // alternatively read from /dev/urandom

echo base64_encode($bytes); // some 44 character string
echo bin2hex($bytes); // some 64 character string

To use as a salt for bcrypt, obviously modified base64 is the correct choice because that is what's expected. But for contexts like account sign-up confirmation key or a unique non-sequential object identifier, which is the correct choice?

I am aware of the random_compat library but this is for learning purposes as well.