When we returned in 2017 and my younger daughter was 4 years old, it was a huge difference (since she was now 36"). The contrast between having 5 moving attractions across 2 parks (including only ONE in Studios) and having 12 moving attractions across the 2 parks made a world of difference. We were able to find a much better balance between things she could ride and things she had to sit out. That 36" mark to me is so key when planning your first USO trip.
I mean this with no offense, but personally, I'm not looking to spend thousands of dollars on a trip to Orlando to watch my toddler play in play areas and splash pads. I subscribe big time to Walt's theory of wanting to ride and enjoy attractions with my kids!

That's why I love MK with 20+ attractions for infants and toddlers to enjoy alongside their older (taller) family members. I think USO is great, I just wouldn't take my 35" child there