Answered by Stephanie, Hiring Expert at Asurion, on Tuesday, March 15, 2016
There are a few points to consider as you try to find the right answer for you: First, what type of career within Computer Science interests you most? It's important to do your research to ensure you're using your time and money in the best way possible. Some roles require a BS, but not a MS. However, be sure to look into the career path of these roles to see if a MS is needed to advance. If your end goal is to be in a position of management, pursuing a MS degree at some point may be necessary.
Also, should you choose not to double-major and instead to pursue the MS degree after your BS, understand that there may be a learning curve concerning the curriculum. MS programs are generally fast-paced and don't always offer much introduction to subjects. To ensure success in the MS level courses, choose your electives during your BS carefully. Intentionally choose courses that offer introductions to the MS courses you might take.
Finally, keep in mind that most MS of CS programs are 2 years in length, which allows time for a summer internship. You can use this time to gain experience you might not have had in a co-op.
Best to you!