DIT University

Hi,
UPES is the best among the three.
At UPES, you have the option of having a specialized domain along with the engineering program.
In UPES, there are 5 options under Mechanical Engineering:
a) B.Tech in Mechanical Engineering
b) B.Tech in Mechanical Engineering with specialization in Machine Design
c) B.Tech in Mechanical Engineering with specialization in Material Science & Nano Technology
d) B.Tech in Mechanical Engineering with specialization in Production Engineering
e) B.Tech in Mechanical Engineering with specialization in Thermal Engineering
So, go ahead with UPES.

https://www.shiksha.com/resources/college-comparison
Check from the link above.

Yes, it's a good choice. DIT-Dehradun is one of the best universities in India.

As per me, you should pursue B.Sc from DIT-Dehradun.

Normally placements are not there in the field of architecture, but yes studying in DIT will land you in a good firm.

DIT University is one of the premier institute of Uttrakhand. They have huge campus, good infrastructure, great faculties and MBA placement were also very good!

Both colleges have good infrastructure, faculties and campuses. Visit their official websites and check last few year placements.