Hi Haresh,
BPC NW is integrated with BW (backend), so if your ERP is already in SAP, BPC NW is the best option.
BPC MS has SQL server as backend. If your ERP is not in SAP than BPC MS is the best option in terms of cost.
Functionality both are very similar, with few exceptions.
Coming to your next question on installing 7.5 MS, it is not advisable to install 7.5 as there are lot of differences in 7.5 and 10. So go for 10 instead. For the MS installation guide please refer
https://websmp210.sap-ag.de/~sapidb/011000358700000469322011E.
Regards,
Kalyan.