When I first saw this feature in the ad, I thought that it's a not very useful gimmick, made for marketing. Guess I was right. I think it would have been more interesting, if SG decided to make variable colours more distinct from one another. For example -first colour is the standard true colour...
ADF is more convenient, protects your eyes better and allows you to work faster. But I would suggest to buy a good one, the one that has a certification like din and din plus.