My most desired Pokemon roommate would be a Delphox. Being an anthropomorphic psychic fire fox, I'd probably be able to get its help with way more kinds of chores than many other, ranging from cleaning to cooking (note I said "help", not "get to do", I wouldn't force my Pokemon partner to do my work for me.) and I'd also be able to play games with them, possibly even video games, which would be awesome since as an only child and with pretty much only long distance friends I rarely get to sit down and couch play with someone.
As far as least desired Pokemon roommate... probably any of the Trubbish, Grimer, and Koffing lines, regardless of form. Normal forms would cause a horrible, poisonous stench (Trubbish and Grimer) or aggravate my asthma (Koffing) at best, while the Alolan Grimer line has to constantly eat trash or I'll start losing furniture to it, and I don't think I make that much garbage. Galarian Weezing might not be too bad though, if possibly too tall.
And I guess if I were to give a "middle of the road" example, probably any of the electric types based off of a mammal, such as Jolteon or Luxray, since they could help you charge things in a pinch, but that might be better served for a "exploring in the wilderness partner" thread.