Hello. IIT Madras has a very good reputation unlike other IITs. It comes under tier 1 university.

When you talk about the branch preference then it totally depends on your interest as well as about what you are passionate about. So choose wisely.

Now coming to mechanical from IIT madras, it offers you wide range of dual degree options, placements better and faculties is far better than IIT Roorkee.

And future prespective for both field is the same. Because both are important to mankind life. So don't worry about that, just concentrate on what will make you happier while learning.

Abroad options for both IITs is the same. Just your percentage and Mark's will play important role while getting admission in universities abroad.

Hope that helps!