Hello Vihaa, 

By IS, do you mean Indian Administrative Services (IAS)? You cannot do a direct comparison of CS with IAS.

The benefit of taking CS would be the high salary. Firms like Google or Apple offer you much higher salary compared to IAS, especially when the IAS officer has no experience. In firms like Apple, you can even join as fresher with very high salary if you have the requisite skills. 

The second benefit of CS is the strong entrepreneurship culture it supports, more than any other profession. And entrepreneurship offers more independence and job satisfaction than working under some authority.

The drawback of attempting IAS would be the steep competition, where Humanities students also compete with PCM students, making the compeition double, whereas undergraduate CS is mostly restricted to PCM students (with a few exceptions).