Choosing which out of Hike or Whatsapp is better depends upon so many parameters which may be used for comparing them.
Accessibility: There are so many of our friends, relatives who are already on WhatsApp but not on Hike. So in order to talk to them, we cannot ask them to install hike first. Thus, in this case, the accessibility and availability of WhatsApp are more than Hike.
Popularity: Both WhatsApp and hike are popular, but for different purposes. The hike may be charming for its nudge feature, while WhatsApp for its video call facility. While hike may have so many emoji, WhatsApp may have less emoji but still simple and commonly used ones. Thus on the basis of popularity, we cannot rate one of them over the other. Still, if we were to choose one, WhatsApp will lead.
Web-based application: Hike does not support a web-based application. But WhatsApp is available as a window desktop for the web-based application.
Offline chat: You can send SMS to a person who is not online through Hike, but not through WhatsApp. This makes Hike more preferred.
Rewards: For every person who joins hike using your referral code, you get a reward. But no such reward is got in WhatsApp.
Media size: while Gmail offers you 25 MB limit, you would be able to send a file up to 100 MB via hike which is not the case in WhatsApp.
Just like fire has its own pros and cons on the basis of which we compare it with other fuels, similarly, Hike and WhatsApp have their own comparative analysis which makes one choose the better of the two as per one's own choice.