I am working in a private bank, a leading mid size bank in local market. We are going to create our core banking solution. Existing solution has been developed on Java using IBM Visual Age 4.0.

It is very important to discuss architecture first, we have currently more than 350 branches working in standalone mode, and it means they are working in self contained environment. They have their own database server (IBM DB2 9.7) and they are communicating with other branches via sockets to send and receive data.

Having experience of .NET for more than 5 years I am trying to convince my superiors to choose .NET platform, but they are reluctant and unwilling. It is my job to encourage them for choosing best available platform to create large scale enterprise application.

In simple word, we are going to create a very large scale enterprise financial application, a centralize and integrated which connects all branch networks plus having scalable, solid architecture that easily evolve over time.

I want professional people to comment on above scenarios. Which platform to choose .NET or Java? Our all resource is currently working in Java, we have homogeneous environment (no Linux, no Mac and no UNIX).

Any idea, any thoughts, any points technical or non-technical i.e. administrative or management point of view will be really appreciated.