I worked with 7.5 recently. That´s ok.
Conecting Tableau to SAP BW 7.3 has many limitations, ex: does not counts number of records, does not generate row ids. Does conection with SAP BW 7.5 improves these limitations?
Could you please explain more, are you referring to use SAP GUI 7.3 when connection BW7.5 to Tableau?