> But reference counting may cause unpredictable pauses when large amounts of objects suddenly need to be freed (e.g. when dropping the last reference to a large array holding many references).

Then again so does manual memory management if you're freeing a large object graph at once.

> At least a carefully written garbage collector can free objects incrementally, and concurrently.

You could get that with refcounting, stashing Rc0 objects in a list of items to free incrementally rather than freeing it all at once and synchronously.