picking 2 top tier houses vs picking a top and middle

Probably since pi Phi is a higher ranked house you have more chances of getting into GPhi over if you were preffed with theta where theta would possibly have you higher on their list since they're middle tier. But I think people are over thinking this too much if you get a bid from GPhi then it's meant to be and if you don't then you'll fit into theta or pi Phi better in the long run. Don't revolve your recruitment around trying to get a bid from GPhi just go with the flow and choose to be preffed with your two favorite houses and just let the system do its thing. If you're able to be preffed with GPhi and Pi Phi then you're very lucky because both are great desired houses.