scatteredInterpolant vs HEG Tool for bi-linear interpolation

Hi,

I am trying to read a MODIS hdf reflectance file in sinusoidal projection and creat a regular data grid (in lat and lon). When I use the 'scatteredInterpolant' function to generate the grid from scattered lat-lon data, it takes about 3 minutes but this same job is accomplished by the HEG Tool in 7 seconds! I was wondering why this is the case and the scatteredInterpolant is so slow here?

Any idea for improvement is really appreciated.