That all depends on your personal preferences! Both have their pros and cons. Indoor and outdoor ones can both be great during the summer to beat the heat. Indoor ones provide a nice escape when it’s too cold for outdoor parks. Plus, many of these have hotel accommodations as well, so you can save some money by staying “in-house”. Indoor ones can be a bit loud since the sound of everyone’s voices and squeals of pleasure are reverberating off the walls. There is definitely more space to spread out at outdoor waterparks. Both can be very busy. Outdoor ones tend to have a lot more attractions to offer since there’s more area.