I prefer carbon for my yanagi. I been working as a sushi chef for over 10 years, I have experience with both carbon and stainless. From my experience, carbon (specially b2 which is my favorite) has more sharpness, I slice hundreds or even thousand slices everyday and still sharp enough. When I use a stainless yanagi (ginsanko) is less sharp after maybe close to hundred slices. It's only stainless that I like is suisin inox honyaki, it's hold the sharpness/ edge retention almost like my other carbon yanagi, but suisin IH more easy to maintain, and keep it clean.
This is just my personal experience. So my advice is go to carbon for yanagi, as long maintaining. Just wipe after use it with wet and clean dry towel. It won't get rust. If you think your knife will rest for more than couples of week just oil it.