I've visited only the shop at 19 Rue Jean-Jacques Rousseau and last time I visited the SA knew by heart what colours the other shop had on different styles so I have only warm memories of this shop Oh and they had quite a few pairs of croc shoes there, gorgeous but pricey.
I know both really well, they don't have much stock, (way less then what you get in the US) they usually complement each other they don't have all the sames styles/colors, you need to ask if you don't want to do both shops to see what the other shop has style and size wise. so they have it trabsferred for you but only the next day. I would suggest doing both!
I went to 19 Rue Jean-Jacques Rousseau during my trip this past week hoping to find something unique or to see if they had the hard to find size 42s. I asked the SA if it was worth going to the other shop for my size 42 specifically and she didn't think it was. They only had 2 pairs of 42s in the store...very plain styles. The styles that were out on display were nothing special that can't be easily found in the US. The SA concurred that I have access to everything they sell there and probably more in the US. I got lost finding it the first day I tried because the road splits and the Rue Jean-Jacques Rousseau I walked down the first day was higher numbers. At that point I was exhausted as I had been walking for hours (tried to skip metro and taxis as much as I could to explore the city streets and get exercise) and my cell phone was dead so I tried again the next day and finally found the right block. Here are pics I took of the shop.