Is IIT Delhi maths and computing a good option if I am interested in CS, compared to taking CS in one of the newer IITs like IIT Hyderabad?

While most people consider MNC as a backup option for CS, you will be surprised to know that the curriculum has more mathematics than computer science courses. 

Curriculum 

• The courses in this program cover topics like Algebra, Calculus, Probability, and Discrete Mathematics, which is an area of mathematics that finds a direct application in Computer Science.
•  It’s important to note that the mathematics covered in the MNC program is very different from what you have been accustomed to at the +2 level and in your JEE preparation. 
• The CS courses of this program cover topics like data structures, analysis of algorithms, and computer architecture. The MNC branch comprises many coveted elective courses like Digital Image Processing and Mathematical. 

Placements

It's the electives you take up that determine your job prospects. The placements are usually spectacular and that should be your last concern. 

• Some students end up working at software companies like Microsoft, Facebook, and Adobe, with similar job profiles of CS with merchant being the most coveted profile.
• Additionally, finance companies like Goldman Sachs, Deutsche Bank, and World Quant, prefer MnC students as their profile is well suited to their requirements. 
• Some students go for consulting too while those who are research enthusiasts opt for higher studies in the field of Computer Science, rather than Applied Mathematics. 

CGPA

• The average CGPA of graduates from this branch tends to be lower than their counterparts in other branches. 
• The workload is quite heavy and there is a lot of coursework.

So, I recommend you to go to this branch only if you are sincerely interested in core Mathematics.