Ah well ya. The first one has some ambient occlusion going on. It's pretty intensive because it tries to emulate the way light works in real life. The second one just does some raycast to cast a shadow. The ambient occlusion however tries to emulate the way light bounces off walls and such which is why it takes so much longer. It's probably doing some other things like reflection/refraction. Give that monkey a semi-transparent/glass material and make the floor reflection and watch how long it takes

Typically it's not the render engine itself, but what you specify/allow the engine to do. The two engines probably just have different default options. Then again like I said I have no experience with Blender so maybe this is its way of allowing you to customize the render output.