Hello aspirant
It depends upon which post are you looking for .You can become an isro scientist by taking anyone of it ,bsc msc physics or computer science .Dear it would be easier if you take admissions in IIST(through jee advanced) . Isro also recruits students from IITs and NITs every year.so doing btech will be more helpful . However for bsc msc candidates it would be better to study from iisc or other best colleges of india .You can become a researcher/ scientist by taking physics . Taking computers is also helpful . Now if you want to pursue bsc msc then I will say physics would be slightly better than cs to become a scientist in isro
Best of luck

Hello Anagha, 

                     Every organisation demands people from almost all sectors to  carry out its work in efficient and productive manner.

                  Thus, for becoming a scientist  u need to get confused with the field to choose as you may definitely become a scientist by choosing any of the above mentioned fields.

              All you need to do is analyse your interest and creativity in any one field in which you can be best and go for it. Doing things out of interest may cause you trouble later. 

 GOOD LUCK