Quote: "while X10 is still the way it was when it came out."
No where near true. If you had x10, you would know the difference between straight out of the box, and v1.09. Plus, TGC is working on v1.10 right now, and have stated that they plan to get x10 to a decent level before they even start work on the Migration. X10 is also supposed to get several exclusive features from the migration, so I've heard. So, X10 has a more support for the future. X9, has all the mods, which are great for performance and scripting (ironsights too) providing a much different experience.
Also, cripex, X10 has plenty of people who understand nearly every quirk of X10 if you'll simply click the bar in my signature.
Either choice you make, they're both quality products of which you'll have many hours of fun creating with.