Both can be used to describe people, with a difference: hilfsbereit means that someone is glad/likely/ready to help. It can, but does not necessarily mean that this person actually does/did something helpful - for that you have hilfreich.
Du warst heute sehr hilfsbereit. You were very eager to help today.
Du warst heute sehr hilfreich. You helped a lot today.
is like when you played well and the trainer tells you "You were very motivated today" instead of "You played well today". And the same way you could have been motivated without playing, you can be hilfsbereit without helping.
Er ist ein sehr hilfsbereiter Mensch. He is always glad to help.
Er ist ein sehr hilfreicher Mensch. (~)
Sounds a bit weird, I'd understand it as so. is always of use. This is why I'd say that your similar task-statement using "immer" doesn't work with hilfreich, either. The other example above is restricted to heute and hence does. Lastly,
Die Notizen in dem Buch sind sehr hilfsbereit.