Stress contours by center stress or nodes stress?

[Bill2001]

In version 2006 of STAAD.Pro you have an option to plot stress contours by center stress or nodes stress which give very different results. which one is more reliable?
Thanks in advance!
Bill

 

[RAYC1]

The nodes stress is more reliable if you also uncheck index based on center stress. This will average the node stress from the plates that touch that node.

You may want to limit the display to the plates in one plane rather than include wall and floor plates into one average. The node stress is better in particular along edges and at corners.