Having tested out both of these bags in person, I have to say I'm not crazy about either of them. I loved the Bottega in its display case, but once I picked it up and started playing with it, my opinion changed. I am a fan of huge bags, but this bag is just too big. Since the leather is soft, the bag gets very saggy. It would be pretty hard to fill this bag up on a daily basis, so there most likely is always going to be a lot of empty space in the bag. And since the bag is not structured, it won't hold any shape. The craftsmanship is gorgeous, and the detailing is divine, I just don't think the bag looks impressive or chic when it is flopping all over the place. Perhaps you do carry a lot of stuff with you. In this case, I think the bag could/would work.
As for the YSL, I don't like the color; it's kind of bland to me. I do like the dark chocolate brown bag in this style, but the tan color doesn't work for me. I was very close to purchasing this bag in chocolate brown, but the filagree handle held me back. The handle is quite shiny, and I couldn't decide if I wanted that much bling on my shoulder on a daily basis. I like the size of the bag better than I like the size of the large Mombasa (XL Mombasa remains my favorite), but in the end I passed because I wasn't completely comfortable with the gold handle. Back to the tan...I don't think the color of the bag really suits the gold filagree handle. The handle is beautiful and it should stand out, and on the tan I think it kind of blends in.
If you are comfortable with big bags and don't mind the potential for sagging if the bag is not filled out completely, I would go with the Bottega. If you don't mind bling on your shoulder and the mild merging of the tan color with the bling, I would go with the YSL. And if you aren't completely sure about either bag, I would take a pass. Both bags are fairly expensive (especially the Bottega) and with all the new fall bags slated to come in the following months, I would hold off on a purchase. Good luck.