DataGrids performance tests

 So my mission is to try to performance test the 3 Flex grids. mx:DataGrid, s:DataGrid and mx:AdvancedDataGrid.

I feel like my tests are incorrect and looking to you to point out my flaws.

Each grid has the same dataprovider and columns defined. I'm only using the default renderers
I have a StopWatch class, that will getTimer() from a start() method, until the next Event.RENDER from the grid under test.
I remove the data provider by setting it to null.
Once the screen is blank, I start the stopwatch and add the dataprovider.

The average of these tests over ten samples is:

Spark DataGrid: 207 ms
mx DataGrid: 176ms
AdvancedDataGrid: 171ms

I feel like my testing method is invalid, as I don't trust that

   1. The ADG is the fastest at rendering
   2. Spark is the worst at rendering
   3. That the difference in rendering between the 3 grids is negligible

Anyone to offer any insight?