Nobu is quite good and will leave your credit card gasping for breath. If you come in to town then the west side has some excellent sushi choices, including Mori Sushi, Kiriko and Sushi Zo.
I've included the right link for the Nobu you are considering in the Bu...
9824 National Blvd, Los Angeles, CA 90034
11301 W Olympic Blvd Ste 102, Los Angeles, CA 90064
11500 W Pico Blvd, Los Angeles, CA 90064
3835 Cross Creek Rd, Malibu, CA 90265
Compared to the other sushi places that you mentioned, how would you rank them? Is nobu good enough foodwise on top of the "perks" (people watching, ambiance). Although I'll be disappointed even if I see celebrities and the food doesn't deliver, I'd rather have really good, knock your socks of sushi that you'll leave the restaurant smiling!
I'll just say that if it were me, and I could stay out in Malibu and not have to hassle with the traffic coming in to town, I'd be perfectly happy with the sushi I've had at Nobu. However, you may be one of those folks who aren't going to be happy with the star tossed Cross Creek clientele that shows up out there? If I were coming in to town in any case I'd go to any of the other three, and I would do so happily. I personally see this as a toss up in terms of sushi.