HI Ripu
Add Row
this method expects us to pass in a sap.ui.commons.layout.MatrixLayoutRow object and it will be added accordingly.
Create Row
this method does a little more. We can pass in a sap.ui.commons.layout.MatrixLayoutCell and it will add it to sap.ui.commons.layout.MatrixLayoutRow object and add to matrix. We can also pass in a sap.ui.core.Control (like list, button, etc) and it will add it to sap.ui.commons.layout.MatrixLayoutCell and then to a sap.ui.commons.layout.MatrixLayoutRow and and to matrix. Or we can also passing a string and it will append it to cell and row and add to matrix accordingly.
This is more of helper method, so to save us effort in instantiation sap.ui.commons.layout.MatrixLayoutCell and sap.ui.commons.layout.MatrixLayoutRow.
Hope this helps
-D