IMO - the upgrade to vehicle lighting is this order:
1) Upgrade the OEM Headlights (if possible, and skip the HID conversions)
2) Install quality fog lights mounted low and wide on the bumper. Ideally the should mounted below the bumper, but on 4x4's they are exposed to damage in this area. They should be installed to come on with parking lights, or parking lights/low beams. Running parking lights/fog lights only may be illegal in some areas, but can make the difference in super thick fog/snow. Yellow/Clear are the best colors for the vehicle operator. Amber fogs are great to use to assist other motorists in seeing your vehicle. (I think the dark amber color reduces the intensity some, so in thick fog they seem more effective) To my knowlege their are no HID or LED fog lights on the market that are true fog lights.
3) The next install is up to the vehicle and driver and would be a "Flood Lights or Cornering Lights" or "Driving Lights or Euro-Beam". Flood lights/Cornerings are great for slowish off road trail rides and illuminate obsticals infront of the vehicles. The beam floods everything in the path. These lights should be wired to operate in conjunction with the brights on thhe vehicle (I like to install a three way switch "On with Brights"; "OFF"; "On" - When the vehicle is in motion you should be able to kill your brights and auxiliary lights in one motion.) These can come in any type of bulb; LED, HID or Halogen. Driving Lights are auxiliary high beams that reinforce what the high beams do, cover the road from shoulder to shoulder out. If you purchase a quality driving light, you should not be able to overdrive it in the average 4x4.These lights can be LED, HID or Halogen. Another thought is to mount these Austrailian Style with 1 cornering light and 1 driving light on the grill guard.
4) The last auxiliary light one could possible use would be spot lights or pencil beams. These are super narrow spot lights that throw their light incredible far down the road. At the distance they are projecting the super narrow beam that will cover the road should to shoulder. With todays technology, I think HID and Halogen are the best and are generally mounted high on the bumper or the roof for maximum reach.