What's the difference between grd 3 grd4 of Ricoh camera?

These two cameras have the same sensor and lens.

The internal processor of GRD4 is upgraded, and the response speed is faster than that of GRD3. The focusing system and LCD screen are upgraded, and functions such as multiple exposure and interval shooting are added. It belongs to the kind of car that looks no different externally, but it is obviously upgraded internally.