The Javadoc for both methods is pretty self-explanatory too:
public boolean performClick ()
Added in API level 1
Call this view’s OnClickListener, if it is defined. Performs all
normal actions associated with clicking: reporting accessibility
event, playing a sound, etc.
public boolean callOnClick ()
Added in API level 15
Directly call any attached OnClickListener. Unlike performClick(),
this only calls the listener, and does not do any associated clicking
actions like reporting an accessibility event.