Prism doesn't assume you are a statistics expert. Prism then presents clear explanations of your choices. Prism also presents an analysis checklist to help make sure you chose an analysis appropriate for your experimental design. SigmaPlot offers help screens that explain program choices, but makes no attempt to explain data analysis options or interpret results. Prism makes it easy to trace every step in your data analysis.
Prism links data to transforms, statistical analyses, curve fits and graphs.
You can easily see how your data were analyzed, and how curves were generated. If you pasted results onto a graph, these will be updated as well. SigmaPlot does not link data to transforms or curve fits. Unless you keep copious notes, there is no way to open a SigmaPlot file and figure out how the data were analyzed. You can't even tell which columns in the data table were data that you entered, and which are the results of calculations performed by SigmaPlot.