Great post title,

I noticed this post was left unanswered so, here's my point of view.

the main difference between both of these is that they are both reactions to an action or a gut feeling in which an indication of something threatening or displeasing is about to happen to you.

Anxiety is based upon fear, a first response re-action born within the sub-conscience, to an over the whelming malicious threat, also it's an attack upon the nervous system whereby fear will freeze you or you will run.

Paranoia is similar though more indicative of something not quite right, or a prolonged suspicion into something that may or may not be a real event or conclusion, as well as being a trap for the victim as the environment will judge you as crazy or talking to the grey.

I in brief give this simplified explanation.