Since I have friends from both VIT and Thapar, I think I can answer this.

Thapar University:

• Thapar Institute of Engineering and Technology is an esteemed institute and among the best institutions in the country. It is considered among the best innovation-driven private universities and technical institutes in the country. After BITS Pilani, it has been ranked as the best private institute.
• The admissions here are based on JEE score.
• There is no management quota at Thapar.
• The placement opportunities at Thapar University are tremendous. The average package at Thapar ranges around 6.7 LPA.
• The faculties at Thapar are great. You will get to learn both practical and theoretical aspects of subjects. The students are exposed to various internship opportunities as well.

VIT:

VIT Vellore is yet to be at par with Thapar University. Since VIT takes in a huge number of students, the placement quality is declining over the years. The average package at VIT is around 2-3 LPA.

Unless VIT Vellore is closest to your place do not opt for it. Thapar University is better in comparison to VIT Vellore. Hence, go for TU without any hesitation.