I like airbrushing and Painter's brushes - they are much more suitable for painting, in my opinion. Also Painter is a cool simulation of various technics - Photoshop doesn't have such features. Another very cool Painter's feature is a colour wheel. It's possible to add special colour wheel in Photoshop CS4 but CS5 doesn't have such option yet. But Photoshop rocks when you have to add effects or to work with layers.