Which is fastest - sFTP or scp?

[Trevor]

If I need to get a file from a remote system, to my local system, will scp get it to my local system FASTER than sFTP?

[shashi01]

@Trevor 

If speed is your only concern and you're moving a small file over a stable network, scp might be slightly faster.
But for anything important, large, or potentially unstable, sFTP is a better, more reliable option.

[Chetan_Tiwary_]

@Trevor One point answer - YES ! scp is faster due to less overhead and simpler protocol. 

Long answer :

• for a single large file legacy scp is usually fastest. 
• for copying many files - rsync will be the fastest due to parallel batching.
• No resuming of interrupted transfer in legacy scp.
• No incremental sync in legacy scp compared to rsync.
• in High latency network - rsync can beat legacy scp using compression as both scp and sftp uses default ssh small window buffers.

anyways, now a days scp uses sftp in the backend unless you explicilty specify scp legacy use:  https://www.openssh.com/txt/release-9.0