In DefaultGroovyMethods.java, a NumberAwareComparator mimics the groovy '==' operator to compare elements against each other for collections operations such as unique(), minus(), sort() etc.
This NumberAwareComparator systematically converts any number to BigDecimal if numbers are involved slowing down very significantly those operations.
By testing first if the elements are comparable and of the same 'kind' to first compareTo() them, we get a cheap but noticeable boost.