Depending on the framework you are using, there are various padding modes that can be used with AES encryption. For example, with .NET we can choose PKCS7, ISO10126, ANSIX923, Zeros or None.
I understand that the encryptor and decryptor need to use the same mode to be interoperable.
What considerations are there when choosing a padding mode? With the exception of 'None', does it even matter which you choose? Can some be considered more secure than others?
Padding None can be used with stream ciphers and AES-CTR in order to keep the ciphertext the same length as the plaintext. Padding zeros cannot always be reliably removed, and so should be avoided. Any of the others can be reliably removed and are fine for use.
Padding None leaks information about the length of the plaintext. Apart from that there is no security implication in the choice of padding. All padding gives the attacker is a partial insight into the contents of the last block. In effect this is a known plaintext attack. If the cipher can't resist a known plaintext attack then the problem is with the cipher, not the padding.
