To begin with, the 5-year dual degree program at BITS is significantly more costly than the 5-year iMTech program at IIIT Bangalore, as well as the 4-year BTech program at IIIT Allahabad.
Second, there's no assurance that you'll get CSE at BITS Pilani if you don't have the required CGPA. So, it will be better to consider IIITA or IIITB.
I have a few friends at IIITB and based on what I heard from them, I will definitely recommend the institute.
The arguments in favor of IIIT B are as follows.
I know several students in the iMTech program who have chosen IIITB over BITS Pilani CSE and BITS Goa, CSE.