It will be busier than a weekday because of HHN that night at the studios. The crowds will be heavier in the afternoons. I don't think you could see a lot of both parks on a single day unless you skip the majority of attractions and shows. October isn't usually busy during the week but on weekends it's busy mainly because of HHN.
Depends what kind of rides you like... More thrill or basically movie oriented type rides?
Tbh you could try to get both done...Like Metro said later in day US will be busier so I would say if you try both get the studios done early and head over to IOA for what ya want to do later at night.