The Original Zone of the Enders is the only reason why this game did not receive a higher score. Repetitive game play, corny dialogue, horrible voice acting, and a surprisingly short single player campaign that maybe last 4-5 hours.
2nd Walker is where the real fun begins. Konami improved on many of the original ZOE short comings. The biggest improvement is the fact that you don't need to return to a previous area 3 times to collect passcodes. Combat is smoother, and more challenging forcing the user to use every aspect of controlling the OF. Voice acting is decent, animation is improved. New pilot that finally replaces the cry baby leo from the first one.
Either way its a great rental, I highly recommend.