I read an interesting article about the differences between these 2 apps recently - one of them that stands out is that WeChat is monitored by the government (like most social media in China) whilst Whatsapp, having been co-founded by a Ukranian with an anti-totaliarian ethos, doesn't actually collect any user information apart from the phone number! And whilst Whatsapp makes money by charging $1 for downloading the app, Wechat does so by selling games and encourages other online shopping.
Google Hangouts is definately the best chat app out... the SMS intregration and using it on desktop platforms with google chrome makes it amazing..
Generally I prefer iMessage (because I can use it from both my computer and my phone), but for people who don't have apple devices I always use WhatsApp. P.S. That inforgraphic is a little bit off. You can totally share gifs, videos, and photos through iMessage.
I installed WhatsAAP last week after its sale and not much of use as my friends on it don't replies to messages there.
Im not too big of a fan on the desktop but google hangouts is the best on mobile. On PC definitely skype though.
I use Viber, its free to use and there is a lot of cool icons and little picture things to send to friends that are free.