I'm the biggest Stevie fan alive, and I still love Vanessa, too!
It's just two different styles. The older Stevie fans don't seem to like how Vanessa sounds so youthful, and writes 'naive' lyrics, and prefer Stevie's rough rock and roll sound. I personally think it's the best of both worlds. Stevie's my faaavorite person in the world, but I like how I can listen to Vanessa and get music that's easy to listen to, and just lay back and relax with.