I need to transfer several 10+ gigabyte files between two internal Linux hosts. The easiest way is to use either the scp or sftp. This will encrypt the transfer which can slow things down. There are several ciphers available that you can use to speed things up. Using modern OSs (Fedora 27, CentOS 7, FreeNAS 11) I wanted to find the best cipher to standardize on. The fastest cipher supported by all of my operating systems is aes128-gcm@openssh.com.

You can use aes128-gcm@openssh.com with scp and sftp like this:

scp -c aes128-gcm@openssh.com user@domain.com
sftp -c aes128-gcm@openssh.com user@domain.com

To use an alternate cipher with rsync use this command:

rsync -avP --rsh="ssh -c aes128-gcm@openssh.com" /source/dir user@domain.com:/destination/dir

Honorable mention goes to aes128-ctr as the second place contender. If for whatever reason aes128-gcm@openssh.com isn't available it would make a good alternate choice.