which is the most efficeint way to access the value of a control

which is the most efficeint way to access the value of a control

of the two choices I have to access the value of a control which is the
most efficeint?
getComponent("ControlName").getValue();
or
dataSource.getItemValue("FieldName");
I find that on occassion the getComponent does not seem to return the
current value, but accessing the dataSource seems to be more reliable. So
does it make much difference from a performance perspective which one is
used?
Thanks I really appreciate the time and effort of the participants to this
forum.