Bachannal vs. Wicked Spoon

We will be in LV mid May, my sister wants to try the Wicked Spoon due to good things she's heard about desserts. I would be good using our free My Vegas comps for Mirage buffet.
I'm a prime rib lover and would be happier to go to WS if they have great prime rib. We will be going on a Sunday and it could be either brunch or dinner. Do both the Sunday brunch and the dinner have prime rib or would one be more likely to have prime rib than the other. Are there any other discounts or coupons(don't fly united so no coupon from there for me) available?

I prefer The Wicked Spoon, the line is shorter or none at all during off hours. I like their selections and I don't feel crowded in their dining area. Another very good buffet is The Buffet at The Wynn.