Kind of depends what you want to do. Arduino/ESP8266/NodeMCU devices are perfect for a lot of SmartHome uses IMO:
-multiple sensors on one device 
https://images-na.ssl-images-amazon.com/images/I/91BKt2sts0L.SL1500.jpg
-LED controllers
-mini web server to view sensors or enable relays
I don’t have a Pi but I think they are over-powered unless you are wanting to do:
-voice recognition
-connect to HDTV
-run a bigger web server
-etc