It depends on your playstyle. Both packs are great.
I love Spa Day for the Wellness Skill, CAS and especially the Yoga Mat. The Yoga workouts give long-lasting moodlets that are great for skill building and career advancement. And when your sim progresses in the skill they will learn to influence other sims' emotions just with a simple friendly interaction. It is quite awesome. And BB has solid content, especially for Spas/Gyms and bathrooms.
Regarding Dine Out, I am not a big fan of running my own restaurant (I have exactly 1 sim who owns a restaurant), but I LOVE having my sims dine out. For example, I have turned the Stargazer Lounge (San Myshuno) into a restaurant in each of my saves and that is my favourite place to take my sims on a date. The ordering of the food and wine, the time they have to socialize, the moodlets. I like it all. Each of my saves has at least 3 restaurants, some have more.
I guess for content and things to do, I may recommend Spa Day a little bit more? But you should think about what you would enjoy more in your game.