Mb hospital during internship is a very good idea.
I dont Understand Why are you so Confusing to choose the Specialization in your MBA Course. Since you have already completed your M.com course in Finance and you are also form Commerce Background, then you can easily choose Finance as Your Major and Marketing as a Minor. You have completed your Course in Finance already, then I think you will not face any problem after choosing Finance, I Think you can easily handle Finance.
If you are Interested to make your Career in Finance Field, then you have to choose Finance and after choose Finance as your Major, you will study Subjects like Security Analysis and Portfolio Management, Financial Institutions, Derivatives Market, Personal Finance and Forex. If you choose Finance then you will Perfect in Stock Markets, Commodity Markets and Other Financial Fields. So there are Lots of Scope in Finance Field because Finance is a Large Area and there are lots of Jobs are availiable for Finance Candidates.
I think Finance in Better then Marketing, Because in Marketing you have to sell the Products, Complete Your Target and Give Innovative Ideas to the Company and Marketing is not Good for all because its required Potential, Capacity and Loyal towards work. If you have a capacity to sell the Product of a company then you have to go with Marketing, but I only suggest you to choose Finance Because you have already completed your M.com in Finance, So you will not face Problem.
There are Lots of Opportunities are availiable for Finance Candidates, So please choose Finance to make your Career better and if you still in Doubt then please consult form your Lecturer or form some Senior, they will guide your better.