I, personally feel (physically & mentally) that manual CPT works better for me especially when I am sick. Doing the chest is very difficult for me when I am sick and if I have an area that shows its worse then others on an xray the manual can concetrate on that area.
WITH that being said....I also like the vest for maintenance. It gives independence (not having to rely on someone or someone else's scheduled) and I like how it relaxes the muscles in my back.
At home I use the vest, but always manual in the hospital!!