Dimensions and bounding boxes
X, Y, and Z dimensions catch scaling and orientation changes. Minimum and maximum bounds also reveal when a model moved relative to the origin even if its overall size stayed constant.
Triangle count
A different triangle count can mean remeshing, decimation, repair, or a geometry edit. Matching counts do not prove two models are identical, but a large change is an immediate signal.
Surface area and volume
Area is sensitive to changed detail. Volume estimates the enclosed solid and can highlight hollowing or wall changes. Open, self-intersecting, or inconsistently oriented meshes can make volume less reliable.
ASCII versus binary
ASCII and binary are encodings, not quality levels. Converting between them can change file size while leaving geometry effectively unchanged.