Well since I wasn't even on this site when this thread started........
Our new rigs have all LED warning and rear DOT lights. Of our two older rigs, one has all Haolgen and one has combination Halogen/Strobe. Personally, I'm not impressed with the visibility of the halogen rotaters on our older rig. The flashers are okay from far away, but the beam is so focused, that they really don't do much up close. The LEDs however have blinding long-range viz and excellent, but not overly bright, close-range viz. On our newest rig we have two small white light modules on the brush gaurd. They are great! I wish we had them in the LED lightbar also. We havent used those untill now because they reflect pretty bad in the snow. (I tried suggesting that we just run all the white lights through a seperate switch, after the emercency master, that kills the white lights only. That way you can have white lights in the system, but you can also have the abaility to shut them off in the snow. We already have one for the headlight flasher. But I am just the new guy, so.............)
On the engine at my fire station, all the lights are halogen (except for two LEDs above the headlights), but there are so many of them it desent seem to matter. Also the reflector configuration is a whole lot better than on the amb. Once again however, the lightbar (halogen rotaters), with the exception of the white rotator in the center dosent seem to have the same eye catching abaility of LEDs.
What really does catch attention forward is the pre-empt/opticom module. Especally if it is one of the larger ones.