whether it's worth cleaning it up would depend on how much the cameras means to you/your family and also how bad is the "damage". is the fungus just on the body?
the nikon em is a relatively inexpensive camera and the cost of cleaning would probably be more than the camera.
the 635 is a good camera which allows you to use both 35mm and 120 film (assuming you still have the 35mm film adapter).
between the two, the 635 is probably worth the clean up
if you don't intend to clean either up, you can still put them on the display cabinet. the 635 is a look looking camera
