1. Less damage to your tyres and the environment when you need spinning wheels to get ETC to kick-in
2. The option to switch-off your ABS and ETC when off-roading - more control for you instead of the the computer
3. The combination of both ETC and CDL, which can be very effective

Assuming that your DII has the actuator knob (see arrow below) on the top of the transfer case then this is a pretty straightforward procedure. Use a flashlight or your finger to check. I understand that the latest DII models do NOT have this. My 2001 does :~).

There are basically two ways to achieve CDL in a DII; by electrical solenoid operation and by manual knob/linkage operation. There are several suppliers of each type, from extremely basic to pretty fancy, (the latter being the use of the DI high low knob and all the plumbing below the knob). I chose what I think is a combination of the simplest to install, most reliable and least costly. Time will tell whether I'm right. I selected a kit developed and built by John Gadd [http://www.roverdude.com].

Overall this job took about 5 fairly relaxing hours, (with just one moment of stress and a snagged knuckle). Overall cost about $170.

The difference is noticeable; much less wheelspin climbing slippery surfaces. The vehicle basically feels much more 'sure' when off-road. Take care not to leave enabled when driving on high friction surfaces.