My personal opinion is definitely Ankha over Purrl (Egyptian cat!). But having a Tier 5 villager just makes your town more unique because not many people like to have them, hence why they're T5.
funny story about purrl. When I was a younger and i played the ac for gc, she was ALWAYS in my towns whenever i reset or anything. When i went into her house i was astounded that she had a bird as a pet (the birdcage) and literally went crazy trying to figure out what it was called. I think i even cried (lol) then one day she built an igloo and we played a game and i won the birdcage. I was thrilled. She still is a favorite of mine, I agree that ankha is way overrated and i think her face is wacky looking. Team purrl all the way!~