GPG & PGP negotiate the encryption & hashing algorithm to use based on the recipient key's prioritized list of supported algorithms. The problem is DES/MD5 are forced to be included as the last choice if not already included due to the OpenPGP Standard.
Yes of course they all are quite secure and perhaps practically more secure than needed (other than quantum concerns or a major math discovery).
However, to maximize security what ordered ranking on gpg supported symmetric encryption would you choose and why?
GPG Supported Symmetric and Hashing Algorithms:
Cipher: IDEA (S1), 3DES (S2), CAST5 (S3), BLOWFISH (S4), AES (S7),
AES192 (S8), AES256 (S9), TWOFISH (S10), CAMELLIA128 (S11),
CAMELLIA192 (S12), CAMELLIA256 (S13)
Hash: MD5 (H1), SHA1 (H2), RIPEMD160 (H3), SHA256 (H8), SHA384 (H9),
SHA512 (H10), SHA224 (H11)
Hashing algorithms are easy to order since SHAxxx family is agreed to be the best in GPG currently followed by RIPEMD160 SHA1 and MD5. It would be nice to outlaw anything but SHA-2 versions.
Riseup's Guide recommends:
personal-cipher-preferences AES256 AES192 AES CAST5
That seams wrong since you want to avoid the DES fall back as much as possible right? Why not this or a reasoned variation?
AES256 AES192 AES TWOFISH CAMELLIA256 CAMELLIA192 CAMELLIA128 CAST5 BLOWFISH
[then DES gets added by software supporting OpenPGP]
Nice answer discussing the GPG but not much on symmetric algorithms.
Top Hashing and Encryption Algorithms