I would say overall, CAS and CoE are looking for similar calibur students and well-roundedness. That said, I do think there is a relative emphasis on math/science for CoE, which makes sense. Also, I'm sure engineering EC's like a robotics team weigh more in CoE admissions than they might in CAS.
My general sense is that in CAS, they are looking for people who were roughly straight A students across the board in all subjects, and whose ECs highlight dedicated passions. In CAS, even most English majors were getting A's in their high school math classes. CoE is also looking for students who were strong in all subject areas, and exceptional in math/science. I'd say Engineering students were strong in most/all subjects, but were among the best in their respective classes in math/science. The math SAT subscore probably matters a bit more in CoE. That said, I'm pretty sure most CAS students who applied to Engineering could be accepted and vice versa.
What really matters in terms of academic qualifications for both colleges is demonstrated success in critical thinking skills across different types of thinking.