Difference between the usage of NWBC and EP 7.31 for ESS/MSS

Hi all,

I have upgraded my landscape from EHP5 to EHP6 ERP6.

Ours is HCM system and already using payroll. We are planning to start ESS MSS in our landscape.

We already have NW7.31 java standalone server for BI portal and planning to use same NW7.31 portal for ESS/MSS. (Also planning to use mobile
application for ESS MSS in future - Dont know anything about this now .)

Recently I read about NWBC and WD ABAP. (I am new to ESS/MSS and not understanding much about this )

Could you please clarify the following questions?

Could you please clarify the following questions?

1. Do I use NWBC or EP 7.31 and what are the main
   differences? (In terms of better usage and less administration effort)?
2. What are the SWC require to use NWBC for ESS and
   MSS ?
3. What are the SWC require to use EP7.31 for ESS
   and MSS
4. What is the difference in WD ABAP and WD JAVA ?

(Note I am new to Portal side and please excuse me if my question looks silly )

Best regards,

Praveen