There are several factors that you need to consider while making a choice.
NIT Kurukshetra is definitely much more economical than Thapar. There was a time when Thapar was superior to NIT Kurukshetra. But with time, things have changed a lot for both the colleges.
At NIT Kurukshetra, the teaching quality varies with departments. Most professors are very learned and supportive. The professors of ECE department are quite learned. However, they are also very strict with their students. The placements are good at both. You can check the placement scenario at Thapar and NIT Kurukshetra .
NIT Kurukshetra and Thapar are both good colleges and have their own strengths and weaknesses.