Currently I prefer to play 2, 3 and 4. Though I do have one Petz 5 baby I still have.
This is not a complete list, the kennel and cattery tend to grow and shrink, so these are the ones I always have in game. I do prefer dali prancing puppies with certain personalities, so they tend to be the ones I end up keeping. All of my main kennel are 2013 or older.
My sweetest baby boy and most prized pet, Midnight. Hexed and received in 2011. He makes me wish that Petz 5 was better, and the main reason I ever boot up the game. He was hexed by Quantaria and was one of several that she adopted out. Its very rare I am lucky enough to own a unique hex and I have treasured him for many, many years now. I have had many offers for him when I do post him places (tumblr/forums/etc), but he will never be up for adoption!