.... As with most apps, it's Horses-for-Courses and each of Facebook / WhatsApp / Instagram have their pros and cons (putting aside whether they are not used for 'moral' reasons).
I did some tests last week with a professional photographer friend who shoots digital Canon DSLR and 5x4 cameras. I sent him exactly the same 2048px longest side 300dpi image both via FB Messenger and WhatsApp because in gifting some of my pics to surfers, I was curious whether there was any difference in delivered image quality. The result was no visible differences whatsoever to the naked eye on a big desktop screen but a substantial difference in image sizes. Surprisingly, Facebook Messenger reduced it the most from 2048px to 1242px/353 KB/72ppi and WhatsApp to 1600px/566 KB. He was interested to know as well and we often help each other.
Btw, WhatsApp is also available (free) as a desktop app for both Mac and Windows - Download from their website:
https://www.whatsapp.com/download
I find this very convenient while using other apps on my desktop Mac.