This was hard! I think that Pets is my favorite of the two, but I had to say Showtime for the actual leisure activities. It's been awhile since I've played TS3, so I may be remembering incorrectly, but I believe Showtime came with new traits and lots which add interactions. Even if you don't want to do the new careers, you can attend sim fest to meet new people as well as watch performances. I believe you can also have your sims level up in new skills regardless of if they are in the career track. Although pets comes with lots of fun objects and such, all the new gameplay seems to be centred around the pets, and therefore this pack is likely not worth it for you.