When viewing and comparing your benchmark result on the "Your score vs the same model" screen there are a few things to note.
This score is an average of nearly all the results in the database, including systems that contain more than one CPU (eg multi cpu capable Xeon systems) and ones that are overclocked. So on multi cpu capable systems (eg Xeon) with only one CPU the result will look a little slower and on multi CPU systems the scores will look closer to the average.
It uses a different script to the result that are displayed at http://www.cpubenchmark.net/ and generally the average result displayed in PerformanceTest will be higher than the results used in the online charts as not as many results are filtered out.