I don't understand why tumblr is so obsessed with slytherin/hufflepuff friendships or relationships. I'm a slytherin and I do have hufflepuff friends but we disagree very often and these friendships are very exhausting. I prefer gryffindors, because they say what they think and they are so much fun or ravenclaws because I think they understand us slytherin the best. Hufflepuffs are nice people but they are not all cinnamon rolls, I think they can be quite judgemental sometimes
I’m really not quite sure I understand the popularity of Slytherin/Hufflepuff friendships/relationships either. I dated a Hufflepuff for about six years, and I can’t even begin to count the amount of differences we had, though six years is six years. Granted half of our relationship was while I still considered myself to be a Ravenclaw, our personalities could not have been more different. Yet I think it was our Hufflepuff/Slytherin common trait of loyalty that kept us together. I don’t think we need another Hufflepuff/Slytherin relationship discussion here, but that is at least my personal experience dating a Hufflepuff.
As for personal experiences, I actually find Gryffindors the most exhausting house for myself over Hufflepuff, both in a relationship and as friends. Saying what a person thinks honestly isn’t something I often appreciate in others and generally Gryffindors have very different understandings of what I personally define as fun.
Some Hufflepuffs can also be exhausting in this manner, but I find most Hufflepuffs are a bit more ‘grounded’ and calmer than Gryffindors. And of course not all Hufflepuffs are cinnamon rolls, and sure… they can be as judgmental as all of the houses can be, but I mean… is that really something to be concerned about as a Slytherin? Hufflepuffs really do share a lot of similarities with our own house.
Ravenclaws are okay as well. As you say, they likely understand us the best (aside from other Slytherins), but that can also be pretty intimidating for a Slytherin who simply doesn’t want to be understood. Personally, most of my good friends are Ravenclaw, but actually they are consistently the most difficult house for me to understand and compare myself to.
Finally, Slytherins are probably my personal relationship and friendship preference. Sharing the motivation and initiative to get things done and understanding standards is really what I value in any of my friendships and relationships.
Long story short: House dynamics are of course different for each person, but it really is baffling how prominent the Hufflepuff/Slytherin pairings are. I have personally experienced relationships with each of the houses and can consider different dynamics, but I will spare all of you from further details.