What type of microscope would be the best choice for viewing living leaf cells? Why?

Compound optical.
o magnifies well enough to view cells. Most simple optical, or dissecting scopes, don't magnify quite enough to resolve cells.
o electron microscopes aren't good for viewing living specimens. Typically the specimen is dead and dehydrated because the stage is in a vacuum. You can read up on live mount stages for electron microscopes, but your specimen is still going to be well on its way to death because of the metal stains used and because of the electron beam beating the heck out of it.