Hello

Doing phd in mathematics from vit vellore is better. Because this institute give you full freedom to choose their supervisor  and their field of study. The funding for their research is same as other government institution . If you are funded lab then you can do better and can also use the facilities  provided.

Professor  here encourage the student and it is one of best deemed university who encourage student to to come up with innovative idea.

Talking about worth than yes it is worth of it if you are interested in.

Good Luck