Overall, I would say that AOT suddenly becoming kosher helps our business way more than competition hurts it.

Then, "JDK9 has AOT out of the box" is a bit of exaggeration. Oracle AOT is only available for Linux/x64 ATM, yields huge binaries and may be a bit cumbersome to use: http://mjg123.github.io/2017/10/04/AppCDS-and-Clojure.html

The main difference however is that a binary produced by Oracle AOT is to a big extent just a pre-populated HotSpot cache, whereas Excelsior JET has been AOT-centric since day one. In practice that means that with Oracle AOT you have to ship both the native binary and the original class files to your customers, and with Excelsior JET you only ship the native binary, which makes reverse engineering your application more difficult.

I recall us being quite surprised when a customer survey had shown that IP protection is more important than application performance for many of our customers, even though it was just a byproduct of our optimization efforts.