While reducing mineral income per base is one thing I think we should be after (and I insist is important), the second part of the puzzle is to remove worker pairing thus introducing a non-linear efficiency curve which is what really rewards people for taking more bases.
IMO, HotS < 4/trip < 6m1hyg < DH10 < LotV < DH9 < DH8 1hyg < BW > anything else I've encountered.