LAS Dataset to Raster: How do I determine the sampling size?

DonaldPirie-Hay1

I am attempting to create a DEM and DSM from a LAS Dataset. I know how to filter the appropriate returns for either the DEM or the DSM, but I am unsure what the sampling size should be (along with Sampling type: Cellsize).

From the metadata I've been provided, the lidar (LAS) files have a horizontal resolution of 0.31m. However, the average point spacing is about 1.3 (for each LAS file, there are only two). Should my sampling size be 0.31 or 1.3?

Any help is greatly appreciated.

Thanks