It is difficult to say which combination suits u. Please take a calculation that helps u
Create a sheet in Excel, and make rows like list of the decisions which u want to take consideration in order of priority for eg. Salary, Career Aim, Technology, Time dedicate urself. And under columns header write options which are available for u like as BI, PI, SRM, ABAP, and so on. Then fill it with points to the best of ur knowledge, and determine which combination comes out the first…. and it is easy to choose for u. It is better to consult with a famous consultant who deals with this kind of subject or u may search on the net and within a moment u can get no of hits from there.
For better info do link here :
Should I do SAP ABAP without any experience?
Future of ABAP