The ones I use most are the Viola, Cello, and Soprano and Alto saxes. They're all excellent so I'd say it's a question of which instruments you like more.
I don't use Kontakt much and don't know it well. The Kontakt-based Sample Modeling horns have good expression but otherwise I couldn't figure out how to control realistic loudness or timbre control of standard sample libraries, so Kontakt seems better suited to MIDI keyboard control. Others who are more familiar with it will probably have more helpful comments.