Tel Aviv is chilled out during the day and a proper party city at night.  The food is great, there is a huge amount to do, or alternatively the beach is never far away.  Jerusalem on the other hand is the capital of world religion, with all the diversity and madness that comes with it.  The contrasts from street to street, moving between Arab, Christian, and Jewish parts, are striking.  Makes for a great place to take a few photographs.