Beijing - Shanghai Train vs. Plane

The distance between Beijing and Shanghai is about 1,100 kilometers (684 mi). The travel time by high speed train is about 4.5-6 hours while by plane is around 2-2.5 hours. For those traveling in a hurry, flight is a good choice while for budget travelers, high speed train is recommended.
 

High Speed Train	Plane
4.5-6h on board	2-2.5h on board
CNY 930-1,067 for first class seat; CNY 553-667 for 2nd class seat	CNY 700-1,800 with a discount
Punctual	Occasional delays
Various land scenery	Blue sky and bird's eye view of two cities

 Although the rail travel time from Beijing to Shanghai is longer than the flight duration, the airports in both cities are located further to downtown than the railway stations. If you include the time of traveling to/from the airports, and for boarding, there is not much difference in the travel times using either the high speed G-type trains or a flight.

 See detailed Beijing - Shanghai High Speed Train
  Note: Time consumed by traffic jam and flight delay excluded.
 In addition to the high speed G ones that travel during the day time, there are overnight connections through either high speed D-trains or normal ones. They save one-night accommodation fee and the day time for sightseeing. They are equipped with sleepers, so passengers can have a good rest.
 See detailed Beijing - Shanghai Overnight Sleeper train
 Usually, train ticket is cheaper than flight ticket. However, sometimes, good discounts may be offered by airlines and the flight ticket can be quite competitive, but this mostly happens in low seasons.
 Flight delay in China happens occasionally due to bad weather and air traffic control, etc. Beijing and Shanghai, as two big and busy cities in China, flight delays occur more. Comparatively, there are seldom delays with the high speed trains because they are not easily affected by weather. 
 Passengers can use mobile devices and the internet freely on rail ride, but on an airplanes, mobile phones need to be switched to the flight mode and cellular data is not allowed to use. If your battery runs low, no worry, electricity sockets are available on the train.
 As one of the Eight Most Scenic Train Rides in China, traveling from Shanghai to Beijing by high speed railway will give you an opportunity to enjoy both urban landscapes and countryside scenery along the way. The fertile plain, vast fields, small quiet villages, tall buildings, bustling and prosperous big cities will leave a deep impression in your travel memory. When flying by air, one can only enjoy blue sky and a few minutes' bird's eye view of the two cities.

 See also:
How to Travel from Beijing to Shanghai
How to Travel from Shanghai to Beijing
Cheapest Way to Travel between Beijing and Shanghai
How to Get from Shanghai Hongqiao Railway Station to the Bund
How to Get from Shanghai Hongqiao Railway Station to People’s Square & Nanjing Road
How to Get from Beijing South Railway Station to Wangfujing
How to Get from Beijing South Railway Station to Capital Airport
How to Get from Beijing South Railway Station to Forbidden City & Tiananmen Square
How to Get from Shanghai Hongqiao Railway Station to Pudong Airport