I find the wolves to have a very wild elegance. I've had Freya in my town back in the gamecube days and she was very interesting to talk to. However, I have Diana in my current town and I absolutely adore her. She's so lovely and sweet, my absolute favourite villager of them all. So... I'm inclined to say Diana.
I like Freya more. I never really liked the wolves, but once I got Freya I fell in love with her. On the other hand, I love deer villagers, but I just didn't really like Diana much when I talked to her, which is too bad because she's really pretty.
they are both gorgeous so you can't go wrong! Maybe look at lots of pictures of both or visit dream towns with them to help you decide. I personally like Diana better, but it's not my town