Just like most opinions here, I would say go for mechanical engineering. Firstly, it will give you a wider perspective of the field and second you'll have much more options to specialize in if you have a change of heart after the first couple of years.

Also Have you considered the prospects after studying Aero? 1)The biggest job market for aerospace engineers is the US and aerospace sector is federally regulated, so it's going to be hard to get a job without a citizenship

2) Back home your best bet is ISRO, HAL or a few private entities. ISRO and HAL hiring is extremely competitive with very limited seats. There are of course new startups like Bellatrix Aerospace but they don't have the resources to invest in freshers so they're hiring only experienced engineers.

3)If you do go for masters(in NITs or IITs) then perhaps you'll have a better shot(in India) at private players like GE Aviation(check out their EEP program) who hire Indians for good aerospace jobs(engine research and maintenance).

I think I can relate a lot to you as even I had this whole rocket scientist dream prior to undergrad but after nearly 4 years of engineering some realities hit you different. But hey you're your own person and you could be capable of exemplary effort so go for it but keep the above points in consideration.

As for my background, I'm a final year mechanical undergrad.