I couldn’t download your data because I don’t have permissions. The usual way to compare data on two volumes occupying the same space but with different grids is to first run Resample With Dataset to first interpolate the fields from one grid to the other. You can then use the Append Attributes to combine the fields of two (or more) pipeline objects into the same dataset. Finally, you can use the Calculator filter to compute difference metrics between the two fields.
You can find more information about this process in other posts such as this one: Superposition effect - #17 by Kenneth_Moreland