I'm glad you have been able to compromise. As a woman in this hobby, I cringe every time I see a "my wife put her foot down here" post. Dogfish said just about everything I was thinking.
As to what to have in the laundry room, if they are going to be QT tanks, holding tanks etc., I'd go with two 20s. The reason being, if you have to medicate a batch of fish you bring in, it's much cheaper to dose a 20g than a 40g. Ten gallon tanks are just far to small for QT tanks, I feel.