First, great thoughts on YSL! You've expressed my mental impressions of this house as well. They have some very unique, and of course, controversial scents. Yet I find them all "wearable." I'd say there's a good chance they are my favorite "designer" house.
As far as my favorite overall, that's a more difficult question to answer. Right now I'd have to say Serge Lutens. I am just amazed at the quality of nearly every scent I smell from this house. I am also amazed at the range this house has. I get a real chuckle every time I read someone write that Serge Lutens makes only thick, sweet orientals, or that all his scents "smell the same." When I read that, I know that they have only tried Chergui, Fumerie Turque, and Ambre Sultan, and then only once or twice.
All his frags seem to have unique character, great development on my skin, and superb longevity. They all bring to mind an image or a story: a place, a time, and characters. Cuir Mauresque is one of my favorite leathers, if not my favorite. Ambre Sultan is my favorite amber scent. Fumerie Turque is one of my favorite tobacco scents. Vetyver Oriental is the most unique vetiver scent I've run across, and my favorite. Miel de Bois is the most astoundingly unique honey frag I've encountered. Borneo 1834 is about the only chocolate scent I like. It's also one of the only strong patchouli scents that I like, or would consider wearing. Encens et Lavande reminds that this house can also do ethereal, streamlined scents. Chene takes me back to childhood, walking in the woods in spring and summer. You want something weird? How about Tuberose Criminelle. Masculine? How about Gris Clair. Extreme animalism? How about MKK. Florals? He's got those covered too. The range is unreal and the quality is always high.
For second favorite, I'd say Malle, maybe MPG, or Villoresi, or Montale...there are so many to mention. But, Serge Lutens hits the most right notes for me.