Replicating a perfume is sometimes seen as pitiful. I understand why: the creation of the perfumer is the main reason people adore these men and women. So may I suggest to change your target: try to analyse what you like in Paris YSL and use that to make a perfume that you like even more.
It Ūs aiming high, because in order to do that you need to:
- get familiar with the most common fragrance materials
- learn to smell in an analytical way
- learn how to mix
A 'recipe' (most perfumers prefer 'formulation') for Paris YSL you can make by yourself after learning the above, and when you do it right the result might be much more satisfactory than simply preparing a copy cat fragrance based on a formulation by someone else.
Comparing the fragrances you mention: I would focus on learning about formulating floral perfumes in a rose/violet direction. Thats what these two have in common.