I would choose the DCC control system based on what your buddies and friends do. Get a system that someone you know has so you can ask some of the questions you will have starting up. Once you get going it won't matter, but sometimes you need some help getting set up.
All the major systems will run any scale. It just depends on how many locos you plan to run at one time. More locos need more amperage. NCE and Digitrax have basic 5 amps systems which will probably run 3-5 locos simulataneously. NCE also has a 10 amp system and Digitrax an 8 amp system if you need more. And if you still need more, you break the layout into "power districts" similar to blocks in 3 rail but much bigger and you add a booster for each one rated at 5 or 8 or 10 amps etc.
CVP( EasyDCC) and Lenz also have good systems. I think MRC is in the business with a DCC system also now. I don't know much about it, but the ads seem to imply it is aimed more at smaller operations and maybe rated 3 amps. I think digitrax has a base system called a Zephyr that is rated at 3 amps also.
After you select the control system, you can pick any "Decoder" from any mfg that you like the price of and that will support the amps the loco draws. Most newer MTH and Atlas locos draw less than 2 amps and many draw less than one amp under load.
