On a front wheel drive (fwd) vehicle, do you put the best tires in the front or rear?

I never run almost bald tires on my car, I replace my tires once they hit 4/32 of tread left. I have always been told that the best tires go up front on a fwd car. Every tire place I went to had no problem putting the best tires up front (but that might change). One winter I had bad front tires and decent back tires (about 5/32-6/32 tread left on the back ones). Every time I would drive in any amount of snow I would slide all over the road and getting any momentum and going up hills was hard. Ever since this happened to me I always got the 2 best tires put up front when winter came around. I was able to drive through the bad weather just fine without any problems. I have been looking up this topic online and there is a lot of debate wether or not the best tires should go in the back or front. Usually the article tells you to put them in the back and people argue that it is stupid. Some articles say the best ones should go up front. I want peoples opinion explaining why. I don't want two word answers (up front, in back). Thanks.