Android Studio was actually built off of IntelliJ, but with features for Android development and a C++ editor for native code. If you've used them both you'll find they are very similar and keyboard shortcuts and muscle memory translates seamlessly. You can use IntelliJ for Android and Android Studio for desktop development, but that's not recommended. The general conscientious on the ftc discord is use Android Studio for programming that involves the phones, but to use IntelliJ for desktop utilities, prototyping off the robot or even just learning things. I'm actually currently working on a Kotlin series, and except for the ftc stuff, I'll be using IntelliJ. For me I'm never unsure which one to use, because they aren't in competition with each other, they are meant for completely different targets. You can even write a library in one and use it with the other.