I would stay away from LED. In a replacement form-factor heat will shorten their life considerably because the current ones available are just one-piece arrangements, but if you look at how the car manufacturers make them, they spread out the components and offer lots of cooling via heat-sinks. Your not going to get space for that in a retrofit. HID conversions are something to look at also. Results might be better. I hear good things about them, and I have then as original equipment in my car. Lasers, you don't have to worry, because conversions will likely never be available and now they are only available on one Mercedes and one Audi each car selling for over $100,000. Also, on these installs there are many pieces, and for these automobiles the units cost in excess of $2500 for the pair.
I'd do halogen if you just want cheap or HID if your willing to spend more.