Brands don't disclose the exact compositions of their perfumes. It could be that they are using roses from other countries, or lower percentages of natural ingredients. Chanel has always made a point of their Grasse plantations for jasmine and roses, which allowed them to control the quality of these ingredients. But essences from different places can be just as good.
In general, you'll find many discussions here about the difference between various concentrations of No 5. It's not a matter of concentration only, the formula is slightly tweaked. The edt is lighter, the edp is heavier and warmer, and the parfum is probably the crispest.