A Boutique and an AD are 2 very different things.
While an AD sells watches from different brands, a Boutique only sells watches from her brand.
A Boutique is a " vitrine " ( a window ) of the Brand, an " Ambassade " in a certain way.
Why d you go to a Boutique rather than to an AD?
Because, at the Boutique, you will receive more informations about the Brand, first.
Then, you will see watches you'll never see at an AD, with sometimes, very nice watches discontinued many years ago, like the Rose Gold Reversos in LE from the 90ies, the Reversos Platinum Nr or 2, and so on...
You may also find here some very exxclusive watches ( whie a very few ADs have them ).
Another very important point is to know that at a Boutique, you will certainly not get a discount, but you will get a perfect service, and you will be treated as you deserve.
To say all, and to be perfectly honest, there are watches I buy at the Boutique, and other watches I buy at ADs.
I don't see myself getting an high end watch anywhere else than at a Boutique, or a very important watch for me.
Discounts are important, but there is more important, sometimes.
A privileged contact with a Brand, a perfect service are also things which count a lot, at least to me.
Best,
Nicolas