Fact: More light is better. This is true with photography, astronomy, and in many other things.  The fact that Digital SLR's have larger sensors mean they gather more light.  That's why they have larger lenses as well. To let more light onto the bigger sensors.  Digital SLR's perform much better in lower light conditions than their equivalent prosumer cameras for this reason.  Digital SLR's have a lot less noise and produce photos that are much cleaner in appearance. 

Fact: Lighting as you learn.  Digital SLR's all provide for some form of additional lighting. On camera lighting is usually just horrible.  Getting lighting off the camera whether from external flash units or strobe lighting is much preferred. A Digital SLR gives you more lighting options later on, and allows you to control that light. It might not seem that important when you first purchase the camera, but as you progress in your learning you will soon see why photography is all about lighting and how you control that light, and not really about your camera. 

The product shot to the left has dimension, and pop to it. The lighting is pleasing. On the right you get harsh, boring, straight on lighting directly from the camera flash

Fact: Better Investment.  Digital SLR's are a much better investment.  Even entry level cameras are at a point where they take photos so well that you don't have to buy the latest camera body to improve your photos.  Most entry level cameras have enough control on them to allow the beginner to learn for years.  That means you can invest in accessories and lenses which are actually going to be even more important than the initial camera.  Buying a $1000 lens for a Digital SLR is an investment because you will be able to use that lens and get excellent picture quality even when you buy a new camera.  With a P&S any investment you made in the initial purchase is depreciated quickly and thrown out when it's time to upgrade cameras again. 

By combining strong directional lighting with a shallow DOF this photo comes out very soft, and draws you in.

There are other reasons why I would recommend a digital SLR over a prosumer super zoom camera to new enthusiasts such as shooting through the viewfinder, manual focus control and the like. But these are some of the reasons I think most people don't consider but happen to be what I think should be the most influential in the decision.