Speed is not a good reason. While RC4 is great for weak chips, like microcontrollers and such, it is actually not that fast in modern hardware, needing at least 4 cycles per byte. The fastest combination of RC4 and MD5 in OpenSSL manages 6 cycles per byte [1].
With AES-NI, AES128-GCM runs at roughly 1 cycle per byte. Without AES-NI, the recent Chacha-Poly1305 ciphersuite Google has been experimenting also runs at between 1 and 2 cycles per byte.
With AES-NI, AES128-GCM runs at roughly 1 cycle per byte. Without AES-NI, the recent Chacha-Poly1305 ciphersuite Google has been experimenting also runs at between 1 and 2 cycles per byte.
[1] https://github.com/openssl/openssl/blob/master/crypto/rc4/as...