Hokuyo URG-04LX-UG01 vs. Hokuyo URG-04LX

Does anyone know what the difference is between these two sensors?
robotshop.com/hokuyo-urg-04lx-laser-rangefinder-1.html
and
robotshop.com/hokuyo-urg-04lx-ug01-scanning-laser-rangefinder-1.html

Obviously one is USB and one is RS232, however is that the only difference? Why does the price jump over $1000?

Has anyone used one of these sensors for a project? We are planning on using it for an autonomous quadcopter that will use the sensor data to use SLAM (Simultaneous Location and Mapping).

Main differences:

URG-04LX:

]Distance: 20 to 4000mm /:m]
]Accuracy:+/- 10mm accuracy /:m]
]Power: External/:m]
]Interface: USB, RS-232C(19.2k, 57.6k, 115.2k, 250k, 500k, 750kbps),
NPN open-collector(synchronous output of optical scanner : 1 pce) /
:m]

URG-04LX-UG01 (newer model):

]Distance: 20 to 5600mm /:m]
]Accuracy: 60 to 1,000mm : ±30mm, 1,000 to 4,095mm : ±3‰ of measurement /:m]
]Power: USB only/:m]
]Interface: USB2.0/1.1[Mini B](Full Speed) /:m]