DC means Direct Current
DCC means Digital Command Control

The answer to this question of which system is best depends on what you want from your control system. If you only have 1 or 2 locos, and only one of them is going to running at a time, and the shunting moves are not complicated, then probably DC would be best for you. The big advantage with DC is that most manufacturers (as at Dec 2005) do not have DCC decoders installed in the factory, so they are designed for use on a DC controlled layout.

DCC is a digital control system, which greatly enhances the realism of operating a Model Railroad. With DCC you dont have to worry so much about complicated wiring, and isolating sections of track! And DCC decoders generally allow extra functions such as turning headlights on and off. Switching moves are generally more realistic with DCC as well, as you can have two locos on the same track, and move just one at a time, whether you have isolating sections or not. With DCC the emphasis is generally more on the operating, whereas DC generally requires more complicated wiring and the switching on and off of different electrical sections. DCC is temperimental regarding short circuits, whereas DC generally isn't. DCC is also more expensive than standad DC.

Another issue regarding DCC is that some DC locos may not be able to be controlled well on a DCC layout, and some DC locos will receive motor dmamage if used on DCC systems.

Having used both systems myself, I feel that any layout (even a small one) can be enhanced by converting a layout to DCC. I used a Bachmann EZCommand DCC system for a whilw, and have found it to be very good and cost effective (about AU$120.00 for the controller). I am currently using a Roco LocoMaus II DCC system, which is expandable and allows programming of decoder Configuration Variables.