Feature to raster Python very slow in ArcGIS 10

Question

I've got an ArcGIS 9.3 script that is also to be used in ArcGIS 10 (but not exclusively).
Under ArcGIS 9.3, this script runs quite fast (<1min per raster), but in ArcGIS 10, running time is dramatically longer (>10min per raster). 
This is, obviously, not acceptable.

The resulting raster has 7349 columns and 6110 rows.

Can anyone tell the reason behind this huge differnce in processing-time (is it because I'm using arcgisscriping instead of arcpy?). 
import os, sys, arcgisscripting
gp = arcgisscripting.create(9.3)

inShape = gp.GetParameterAsText(0)
outRas = gp.GetParameterAsText(1)
field = gp.GetParameterAsText(2)
cellSize = gp.GetParameterAsText(3)
snapRaster = gp.getParameter(4)

#Storing old snapping parameter
oldSnap = gp.snapRaster
#Define snap raster 
#define extent
gp.SnapRaster = snapRaster
oldExt = gp.extent
rasDesc = gp.Describe(snapRaster)
newExt = rasDesc.extent
gp.extent = newExt

#Conversion
gp.FeatureToRaster_conversion(inShape, field, outRas, cellSize)
gp.snapRaster = oldSnap
gp.extent = oldExt
del oldSnap, oldExt

ChrisSnyder · Answer

True - My forays into v10 arcpy land have not been very encouraging.

ArcGIS v9.3.1 remains my geoprocessing workhorse...

MathewCoyle · Answer

In my experience, when migrating scripts from the arcgisscripting module to arcpy, a lot of issues can come up.

When running an arcgisscripting module script in an Arc10 environment, there was a noticeable loss of performance in terms of speed of processing. Compared to running the same scripts under an Arc9.3 environment.

When testing using both arcgisscripting and arcpy modules in an Arc10 environment in the same script, there were severe performance impacts and instability.

Conclusion I found: It was be easier to write a separate script for Arc10 and Arc9.x than to try to make the same script compatible under both environments.

ChrisSnyder · Answer

Is it faster if you comment out the gp.snapraster line?

Also, I notice you are setting the extent of the new raster to be the same as the snapRaster... Why not set the gp.extent = to that of the inputShapefile and then set gp.snapraster = snapRaster? By setting the gp.extent = the extent of snapRaster, you don't need to then set gp.snapraster = snapRaster.

Could it be that the extent of the snapRaster is much more expansive than the extent of the inputShapefile (and therefore has to take a lot of time to produce a bunch of extra NODATA cells on the periphery)?