>>1395288They are different. /r/waifu/ is more for casual waifuists and mostly consists of shitposts, like most of /bant/. /r/waifuism/ is for people in committed and dedicated relationship with their waifus. They have some pretty strict rules with regards to what you can and can't do with your waifu. People there take their waifus so seriously it's scary at times. Interesting drama pops up from time to time though.
