Both the colleges are good because both are NITS.But if we are talking about ranking then NIT calicut must be better can vnit.If we are talking about placement then VNIT placements are some good companies are visit such as -EXXON mobile,Reliance,Sun pharma,pedilite,pepsico,Godrej,L&T,Lafarge etc. If we are talking about NIT calicut then here is also placement is good but not good as VNIT here is also some good companies are coming such as- Reliance, Murugappa,BPCL etc. Here is the link if you want to know in detail. as-https://www.quora.com/How-are-the-placements-for-chemical-engineering-at-VNIT-and-what-is-the-average-package/answer/Ajinkya-Bhoskar?ch=10&share=8b7fd9bf&srid=u5PQ3
https://www.quora.com/Nit-calicut-placement-for-chemical-engineering/answer/Gautham-Kuttu?ch=10&share=5fa77187&srid=u5PQ3