Not hugely familiar with Tolkien's trolls. But, I have to say, koloss can be up to thirteen feet tall and wield weapons fitting of their scale. They are not naturally well-organized, but they can be efficiently directed in combat provided the right kind of commander.
In a long term battle, I would also wonder whether koloss can spike trolls. If so, then the koloss would undoubtedly win, slowly assimilating their enemies into their horde.