I didn't realise that WhatsApp can be used like Skype, I'll give it a look.
I find Skype useful because I can phone family and friends and can 'show them around 360 degrees' as we speak. It was really useful on my Keswick to Edingburgh hike a few months ago, I showed a USA friend live pictures of me walking beside Hadrians Wall and a few days later exploring an old castle, he was so impressed. A real castle and a real Roman Wall, nothing like that where he lives. Also useful if my wife wants to send me some typed information, or for me to view a document. I can also use it if I'm recording my route on Wikiloc, the app allows me to send it in real time via Skype to show her where I am and where I'm going to. And if I want to be really boring I can also show my wife the restaurant I'm in, a good look around my location and me drooling over the food and wine. I've only used it once to show my little nephew what problems I was having trying to make my way through a herd of cows who didn't want to move when I tried to get over a stile. Made him laugh evidently!
I've just had a look at the reviews on these type of apps, seems to be a bit samey, it looks like I'll stick to what I know.