I greatly prefer Agent S over Bluebear due to Agent S having a more unique design. I've had her in one of my towns in the past, liked her, and only got rid of her because she didn't fit the town theme I had established. Also, if Burumun is correct in their assumption that you might have or might want Kid Cat then it would also be nice to have both of them. If not, then that point is moot, but yeah.
Agent S is much cuter in my opinion, Bluebear was the only animal I thought was the opposite gender than what they were (Not that it's an issue) I just can't unsee what I saw for my younger days lol, plus I really dislike peppy personalities.