Symmetric cipher speed (AES vs Camellia vs Twofish)
Just use AES. It's hardware-accelerated and implementations have had ages to have flaws discovered and patched. More strongly, just use GPG to encrypt data at rest and just use TLS (>= 1.2, with appropriate AEAD ciphers) for data in motion. "If you're typing the letters A-E-S into your code, you're doing it wrong."

Anything you build yourself is infinitely more likely to be broken as a result of your design choices than by your choice of cipher.