I have a option to choose between two versions of Norton Security. Which one should I buy? (i.e. Version 2016 and Version 2017)
In simple terms, any software's higher version brings improvements with new features if compared to the previous version. With Norton Security, the possible reason to buy a lower version is because of lower price. After purchasing and installation of the product, the software can be updated to the latest version as Norton Security users have privilege to the latest version as long as their subscription lasts. So, if there is an opportunity to purchase the very old versions (like a version from 3 or 4 years ago), it would be important to cross check with Symantec's support if such version is entitled to free upgrade in to latest version. Although, purchasing a previous version is not an issue.
In case, if you require assistance in picking the Norton software amongst the current Norton products, check Norton Software Selection Guide page.