I'm agree with JamesD, Groups2 is a macro and already is a complicated code, I don't think that Groups2 can grow much more (add more features).
Sessions is a kplugin that can grow a lot, but it isn't developement enougth yet.
The Macro language have more limitations than C++ language used in kplugins.
Now you can use both or than you like more. If you ask me about the future, I think kplugins are the future.