CSM: Maulerfiend vs Helbrute/Dreadnought

This is one that has had me a trifle puzzled of late.  Which is better: a Maulerfiend or a Helbrute (i.e. Dreadnought) for Chaos Space Marines? To do a fair comparison, let me firstly note that a helbrute with a pair of powerfists costs 20 points less than a maulerfiend with its pair of powerfists.  They both have the same number of attacks, but the dreadnought has strictly the superior stat