SFTP vs. SCP and transfer rates

[Steven N. Fettig]

I know this question doesn't relate directly to FreeBSD, but because I 
use both sftp and scp on FreeBSD systems constantly, I thought someone 
here might know.
If I sftp into a server and get a file, it usually transfers at about 
1.2 KBps - regardless of interface, machine speed and connection speed.  
If I transfer a file via scp, it transfers at around 6.5 MBps on a 
gigabit link.  If the link is slower, it still transfers at a rate many 
multiples of my sftp transfer.  Is there a reason why one form works 
faster than the other?  I remember someone once mentioning that sftp is 
really designed to run at a much slower rate than is available on many 
intranetwork connections these days.  If this is true, is there a way to 
make changes?  Is scp also limited by a number of speed factors?  
(Because even though it is much faster, it still is not necessarily 
moving at a speed my network gear is capable of.)

TIA,
Steve Fettig