Going back OT, both Xi'an and Yangshuo have their attractions. It just depends if you want a city break or a countryside one.

Xi'an: Lots of history, shorter time to get to (and you can take the sleeper/bullet train), the Warriors (allow 4 hours), cycling on the city wall (hire bikes up there), climbing the pagodas. Visiting "Muslim Street" is a great evening activity - so much going on. The mosque there is also amazing.

Yangshuo: Come here to escape the worst of the pollution (Xi'an is heavily polluted). Perfect for outdoor activites, cycling, walking, boats, climbing, caving etc. Good for shopping too. Massive variety of restaurants. Too far for the train (24 hours), but there are lots of flights (around 2.5 hours) so easy for a night or two. And of course, the scenery is World Class. Guilin is the big city version of Yangshuo. Skip it, and get a taxi straight from the airport (KWL) to Yangshuo.