I'm a civil engineer (10 years experience) but have worked with construction folks in the past when they build my projects.
A construction management job involves more construction plan reading, delegation, scheduling, budgeting, etc - essentially your job is to make sure the job gets done on time and on budget and coordinating the necessary resources to accomplish these goals.
A construction science job deals more with the actual design and construction of projects - you're looking at the finer details of a job.
Regardless of which major you choose, the bulk of your construction career learning will take place on the job through doing actual work and training. My guess is that these 2 majors have similar classes. You can always transition to management during your career, if your supervisor thinks you are qualified.
Darren recommends the following next steps:
- Compare the classes of each major to see what material appeals to you more