In/Out takes things in and out of the various contexts (application, session, conversation and event/request).
The get/set stuff you pointed out does much the same thing but it does it on your backing bean. So the lifecycle of that variable depends on the backing bean itself.
In general, I tend to use @In/@Out for entity beans and things that are in the session scope (like "currentUser"). For non-persistent things that are specific to that backing bean (like say, a verify password form input), I sometimes use get/set.
In some cases, it doesn't make a difference.
They are very different. One is for inter-component collaboration, the other is for accepting user input fom forms.