In my point of view, the transportation in xi'an is not so good than its in beijing.

The buses: In most of time, the buses are always crowded especially for the hot line to the center of the city.

The taxi: The taxi in xi'an are all very fast and crazy, but anyhow they are cheaper than other cities'.

The buses to the famous places:There are too many buses to the places, the government will organize enough buses for the tourists so we'd better to by the buses which are organized by the government owing to its safe and convenience. Although the waiting line is very long(about 1 km), you will get on the bus in 20 minutes because of the organizing of the government, and everyone will has a seat.