This is a very long topic, but it is worth reading or at least a skim:
I work for the government, so i am in a similar situation in that i need to justify, in writing, why I am using anything other than the absolute cheapest solution available.
Like @brandon1 mentioned, the unlimited version is huge, if you even can price that out with the other guys it will almost certainly be cost prohibitive. To your point, there definitely is a learning curve, and its typically steeper, but on the upside you gain access to some extremely powerful tools.
I haven't reviewed VTScada's licensing, but that is another major consideration. Ignition's support is excellent, and very reasonable.
Overall, I think it absolutely worth it taking on python, css, sql etc. but im an ignition fanboy and love learning these new things.