Today I gave my friend Eric two Michel Cluizel milk chocolates to taste. The chocolates are very similar in their levels of cacao (45% and 47%) but have different bean origins. Michel Cluizel's 1er Cru bars are each made from single estate beans from a different plantation, and the Grand Lait is blended out of several different origin beans for taste. Here is what Eric had to say:

Michel Cluizel Grand Lait 45% Harder to the bite. Once it melts it gives that slight cooling sensation, and feels smoother to the tongue than the other. Taste in general chocolaty.

Michel Cluizel 1er Cru de Plantation Maralumi 47%
Very slightly darker in color.
Does not have that cooling sensation.
Taste-wise, it's different from the other in having a slight tart, fruity
quality.

Both are pretty good.

Michel Cluizel's lines make for very interesting chocolate tastings. Single estate bars go a couple steps past straight up single origin bars in that the cacao beans are not only from a single country, but from a limited area with the specific soil, conditions, and the unique growing style of a single cacao plantation. Cluizel is really into creating ways to understand the nuances of different cacao beans. In addition to the 1er Cru de Plantation tasting box, Cluizel also has a Les Nuanciers tasting box series, with a "High Cacao Contents box", a "Pure Origins of the World" box, and another called "Once Upon a Bean."