The GST's I've used go into neutral during a shift (which takes 1-2 seconds).  It can be a surprise if you are on a slope with a load.  On a place that's flat, you might never notice it but if you have a lot of slopes it could be an issue.  Maybe the new ones are better on this point?  Other than that, I think GST is superior for callibrated spraying, or other jobs where exact speed is important.