[usernam]

For what I see, the first and foremost initiating factor for a statistical package is education, and second it's available methods/packages. You have universities where you can clearly see that the predominant taught package is Stata, or R (and in the latter, the choice of UI is mostly arbitrary).

In the end though, unless you want to reimplement methods, you can count on having R packages for any method you can think of.

Few statisticians though spend the time to evaluate different IDEs than what they where taught. I've "converted" many still using Rwin.