Buffer depth,frame rate,finite focus control,metering and the ability to pick/choose function interpolation(s) and ISO handling capabilities...are all 100% functions of the body. Hint.
The 7D is a Lemon,with nothing redeeming in it's regard.
Once you taste a killer body's resolve,it will ALL make sense. Until then,you are trying to see,what you can't picture. Pun intended.
Backing up is easy,adding "reach" is not.
Hint....................
