In Kotlin 1.1 you can use contentEquals and contentDeepEquals to compare two arrays for structural equality. e.g.:
a contentEquals b // true
b contentEquals c // false
In Kotlin 1.0 there are no “built-in functions to the Kotlin std-lib that tests two arrays for (value) equality for each element.”
“Arrays are always compared using equals(), as all other objects” (Feedback Request: Limitations on Data Classes | Kotlin Blog).
So a.equals(b) will only return true if a and b reference the same array.
You can, however, create your own “optionals”-friendly methods using extension functions. e.g.:
fun Array<*>.equalsArray(other: Array<*>) = Arrays.equals(this, other)
fun Array<*>.deepEqualsArray(other: Array<*>) = Arrays.deepEquals(this, other)
P.S. The comments on Feedback Request: Limitations on Data Classes | Kotlin Blog are worth a read as well, specifically comment 39364.