The SD9 and SDVE are the exact same gun (minus the finish and sights) and both have a good degree of play in frame to slide fit when compared to the Sigma. As I mentioned in other posts I believe its due to the rear rails not being attached to the frame. Not sure what the OP means by stating the SDVE trigger is better than the SD they are exactly the same trigger and sear.

Here are some pics of my Sigma and SD to show how the rear rails are not attached to the frame