Hi I will share my experience about facebook messenger. First of all it is android, ios, and microsoft appliction. Different operating system have different sizes. I used in my android mobile. Its size is very high. It takes more storage capacity when it is installed. When installed Facebook messenger the mobile becomes slow down. It takes huge amount of ram.
I recommended to not installed this app on low ram capacity mobiles. Its icon is nice design. And for those who have high ram capacities like 1Gb, 2Gb and so on. It is better for those mobiles which have high rams.