I am a lecturer in the Brunel intelligence program. Take a look at the website, faculty and taught components; compare them to what you find in other programs. Decide which is the best fit for you.
Each security-oriented postgraduate program has strengths and weaknesses. Each has a comparative advantage relative to other programs, usually based on the knowledge/experience of the faculty. There is no "best" program; rather, each student should decide which program is the best for him or her, depending on what he or she wants to learn and where he or she wants to go after graduating.
For example, KCL teaches intelligence studies within a broader security framework. Brunel, on the other hand, focuses more on intelligence studies as a specialization. Which approach would be best for you? Or would you prefer a more historical approach to intelligence studies, as per the faculty specializations at Aberystwyth (intell studies specialization) or Warwick (intelligence studies within international security framework)?
Also, where you go after acquiring the degree is up to you. A prior poster was incorrect in describing Brunel's intelligence program as a better foundation for those who want to get jobs in the field whereas KCL is better for doctoral work. Instead, I could easily argue that KCL's MA in Intelligence and International Security could help someone get a job, while Brunel's MA in Intelligence and Security Studies could provide the academic foundation to go for further (doctoral) study. In fact, Brunel has a handful of students pursuing doctoral studies with intelligence studies specialization. It would be better to say that either program could help prepare you for whichever direction you'd like to go in the future...
Similarly, the question you ask about specialization (IR versus intelligence studies) depends on (1) the interests of the student in question, and (2) purpose for taking the course.
See writings that address intelligence studies as a postgraduate specialization:
About Intell Studies in UK:
Goodman, Michael S. "Studying and Teaching About Intelligence: The Approach in the United Kingdom." Studies in Intelligence 50, no. 2 (2006): 57-65.
About Intell Studies at KCL:
Goodman, Michael S., and Sir David Omand. "What Analysts Need to Understand: The King's Intelligence Studies Program." Studies in Intelligence 52, no. 4 (Dec. 2008): 1-12.
About Intell Studies Brunel:
Davies, Philip H. J. "Assessment BASE: Simulating National Intelligence Assessment in a Graduate Course." International Journal of Intelligence and Counterintelligence 19, no. 4 (Winter 2006-2007): 721-736.
About Intell Studies in Canada/US:
Rudner, Martin. "Intelligence Studies in Higher Education: Capacity-Building to Meet Societal Demand." International Journal of Intelligence and Counterintelligence 22, no. 1 (Spring 2009): 110-130.