Sometimes a large portfolio can be almost overwhelming to a client. If they get in there and start seeing a lot of examples they might think your just trying to show off. Its a good idea to only use your best work and like steveb said the work that you loved but the stupid client hated. Also your site its self is a portfolio piece. So the look of your site is going to way on your clients decision as well. I think it would be a better idea to keep them on your site rather than sending them to all the work you have done. Just my thoughts.