When is it preferable to use a Dialog box as opposed to an Activity in Android? From my understanding, anything you can do with a Dialog box you can also accomplish with an Activity. Are there any tasks that can only be accomplished by an Activity or a Dialog?
Is what you're doing worth a new Activity? Do you need to be able to start it through an intent? Do you really need to create a new Java class for it?
If it's a straightforward dialog that displays a text and has simple hooks for positive/negative/dismissal functions, definitely use a dialog.
If you have something complex, you may want to go for a full-blown activity.