Rihanna (S.O.S, Umbrella, What's my name?, Man down, We found love, Diamonds) Katy (Hot N cold, Waking up in Vegas, Cali gurls, Teenage dream, E.T, Roar)
Hmm..maybe Katy? I know she's really into themes in her music. Nearly all her videos in the teenage dream era were cute, different yet cohesive. In fact it was one of her main selling points. I can see Rihanna having some good video's but running out of steam and having a few filler video's a la Monster.
Katy's videos are always well produced but lack any sort of elements that really tie back to the music. It's always more of a separate entity and never really matches her song's vibes.
Rihanna, however, is quite talented at creating a visual/musical body of work, so her
probably Katy, she consistently brings out great videos while Rih has some pretty average ones...
the TD era was pretty close to one anyway since like half the songs got videos