Sorry for 'bumping' this quite old thread, but I eager for answers as well.
Been suffering from slow SFTP x-fers ever since day one.
Also in my case the speed penalty is around 5x.
Is this really normal? Quite confusing, I must say.
Also, SFTP is much slower than FTPS, which also is a secure protocol.
Any explanation with or without reference links would be much appreciated.

Ty in adv~