Hey John,
So, if Sean or any other Actual Rules Marshal wants to correct me on this, feel free, but:
Fear and Paranoia are mechanically different enough that the roleplay should, consequentially, be noticeably different. Fear requires the PC to attempt to break the line of sight of the thing that caused it at all costs, unless doing so creates a safety hazard; paranoia does /not/ require this, only that you must RP your character's utter conviction that everyone is plotting against them.
So, you know, Fear? Run screaming. Paranoia? Refuse to let anyone see your back, tell them you don't trust them, back yourself into corners - there are a lot more options there than "I must now fling my screeching, useless body across the field".