In the laser hair removal field ... which skin type would take a good results if they treated by this technology? The dark or white skin?

white skin and dark hear are the best for laserhairremovel.

The contrast between hair and skin has to be big.

years experiance with laser and ipl and electrolyse

Earlier it was only fair-skinned people with dark hair used to have good results. But today, with the advent of new lasers e.g Yag laser machine hair removal is easier for all skin type. Although this fact should be kept in mind that darker hair responds best to laser hair removal. If the hair is light (e.g. white or very blonde) or red, it may take more sessions to get results.

both skin types would respond to laser hair removal 

white skin or lighter skin

both skin types has its own respective machines (like yag machine for darker skin, and alex machine for the white ones). And wether of these two skin types is receiving good result in using this kind of technology. Also it depends on how regular you are doing the session. the more you do it regularly, the better result you would get.

White skin with dark thick hair is the ideal case

Dark skin

The white skin definitly but with dark hair.