Hi Sandeep !!
Firstly a big congratulations to you for making it to both these institutes
See if you are interested in hardcore research abroad , then go for CDS. And one more thing , just look at its brochure to locate the subjects. Viv told me that CDS doesn't focus on game theory. So if this subject is of concern to you , then you may skip CDS.
Jamia is good. As Mphil has mentioned , if there is a scope of placement , then Jamia will provide you the flexibility of taking up either a job or research. On the other hand , CDS has negligible in campus placements. But since it bears a JNU tag , it may provide an advantage off campus. Not sure, so will not comment on that.
Jamia is in Delhi , so Iam sure it must be in your comfort zone. So now just estimate , the opportunity cost of going to Kerala
Wishing you all the good luck and success !!
"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."