I imagine that the 6-quart would be great for double recipes but it is
not as good for single recipes. The problem comes in with the
proportions of the bowl and paddle and it does not mix the bottom of
the bowl well. (Granted, the mixers are never good at that) but this
one is worse...if you are going to hang onto your 4.5 I would say get
a 6 as well but if you are looking to just have one...I would get the
5 quart with the larger motor.