Which alzheimer's drug is most effective: Aricept or namenda (memantine)?

Early vs later stage. Both relieve symptoms of the disease & focus on neurotransmitters key to memory and learning. Aricept focuses on acetycholine in an attempt to slow its loss because of alzheimer's. Namenda (memantine) focuses on glutamate, blocking the excess produced as a part of the disease. Namenda (memantine) is better suited to moderate to advanced stages of alzheimer's, while Aricept is for early onset through advanced stages.
Depends. Both drugs belong to different class due to specific activity of mechanism for slowing down the progression of alzheimer's disease. The decision to pick either one of them or both is based on the individual. The key to make both drugs successfully is to have socialization and to keep busy for activities.