Another thing to keep in mind with the string follow Shelton, there is less pretension on the limbs so the initial pull is easier and builds up smoothly till the larger back muscles can handle the final draw weight. I like this in a hunting bow and it helps if you have shoulder issues.
I have NM Whisper, Shelton, Classic and Ramers and the difference in speed is negligible all else being equal. Your shot to shot variance is probably greater. I can shoot a 60 lb Ramer or Shelton easier and longer than a 55 lb recurve or hybrid for example and the performance is about the same especially with heavy arrows.