Well, yes. Cohabitation is always more efficient than living on your own. And the difference per head is essentially just 5m^2, I bet my balcony that's almost useless takes up about that much.

And renting or buying, I would always go for an apartment. I just do not understand houses. If I wanted more room, I'd go for a bigger apartment ... like those fancy 2400+ft^2 two-storey apartments.