not wanting to sound rude, but if you are both unsure of the hd projector market, why are you helping/ being asked to help your friend.
My reason for asking is, installing a projector system will demand compromises. For instance, a temporary system, i.e. projector on a coffee table, temporary fold out screen is a faff if it going to be used regularly and needs somewhere to store it when not in use. A permanent system with fixed mounting of the projector and motorised screen involves room compromises, possible decorating/ light structural work and potential difficulty in hiding wires etc.
Your friend is the only one who can work out which of these options is preferable. They need to talk to the experts and come to the decision themselves once they understand the pros and cons of the situation.