I planning to write an application in which there will be a service (call it A) listening for particular commands. This service will then relay those commands to other services (call them B and C) which are written, respectively, in .NET and Java (service A chooses which of service B or C to which to relay depending on the contents of the request to service A).

I am looking for a framework that will allow for interoperability with both .NET and with Java, for example WCF or JAX-WS, or writing a custom framework (e.g., JSON REST commands over HTTP, similar to http://code.google.com/p/selenium/wiki/JsonWireProtocol).

What questions/aspects should I consider in deciding?