That’s a good question! 
WiFi plugs are often inexpensive to buy which is good. However, they use significantly more energy to operate over a year, they take up an address slot on your router, and they don’t help strengthen the mesh for your battery-operated sensors and locks. And of course most of them don’t have direct integration with SmartThings.
They can be a good solution for some people in some rooms, but most people using SmartThings, which is who this forum is for, will probably choose zigbee and/or zwave for a whole house solution.
In this case the OP has mentioned 35-50 devices. Many home WiFi routers only handle 32 devices, and that includes all your mobile phones, tablets, laptops, game players, streaming boxes, etc.
WiFi is great for a lot of things, including streaming audio and video, but for serious home automation the other protocols are usually considered first.
The exception is if you want a smart plug you can reboot even if the smartthings hub is not working. Many people use a single Wi-Fi device for that purpose. Choice is good.
See the FAQ (this is a clickable link):