I don't think there's any real world direct equivalent to the war in Sol. I think a more ept comparison would be something like the United States (GTVA) vs the European Union (UEF). The US has a vastly larger and more advanced military compared to the European Union and much of it is spent on power projection across the globe. By comparison, the EU's militaries are primarily concentrated within their borders, with very limited power projections. Economic-wise, the US and EU are comparable in GDP, reflective of the GTVA and UEF. If given time to prep for a war, the EU could certainly match the military power of the US. But if the US invades immediately, then the EU won't have a chance to mobilize.