Imo, Felidae.
In all honesty, (I'm gonna laugh if I get bit for saying this) I hate the Warriors series. It's so... unoriginal.
Warning: Rant Below.(Offtopic: I wish we had a spoiler button, lol.)
I mean, the names, for example. You take two things and put them together. Not too creative if you ask me. But in Felidae, I guess the names aren't as creative but they're better than smashing two random words together to get a name. And as Aazzi said, the Erins can get too descriptive with things you don't need to know about, and then when it comes to something you should know about, they don't get descriptive enough. That kinda irritates me. There are some parts in the book that are of no importance at all. And then there can be another one that can make a huge difference, and you don't get enough detail of what's going on. I don't mind if you describe the scenery, just don't go too overboard and forget to describe something major that happened in the story. And not to mention that the books repeat themselves way too often.
Rant Mode: Off.
But that's me. I guess Felidae is somewhat of a cliche as well, but it did come first, after all. So, all in all, I have to say Felidae.