Just get both. It helps better to get a deeper idea in case one of the textbooks just skim over a certain topic. I use both textbooks as well.
For physics, In focus is better at explaining, but Pearson is better for a deeper understanding. Questions are good in both.
And same for chemistry, but you're better off doing practice questions from past exams, whilst the textbook is good for content.
For Maths Adv, I think In Focus is good, but your better off doing past exams and hsc questions for practice instead and watching videos for understanding.