I think spa day is better than outdoor retreat tbh. It's a bit niche but I can't count all my sims that do yoga on one hand (love the classes :D) and I think it's a nice way for sims to just relax, and meditate on what's going on in their lives. Although I do like to put spas in granite falls so these two work pretty well together (making OR a lot better to me :)). All in all, I would probably be hesitant to buy spa day if I had a smaller budget but it's one of my favorite TS4 packs for some odd reason, so I really don't regret owning it :)