Hi tomo......the old dc system will energise the whole track system unless you section it....basically that means if you have six loco,s on a piece of unsectioned track when you turn on the juice they all move.....more than one controller on the same piece of track requires cab control which effectively gives control to one or the other controllers.......i.e they have to be insulated from each other.
Moving individual trains or having more than one loco on unsectioned track is a job for dcc..........no sections ...simple wiring.....and the ability to double head or bank long trains without having to actually couple to the train.so at the end of the assist you just decrease the power to the banking loco and it will gradually fall away from the back of the train in a prototypical manner.
I have just switched over to the hornby elite dcc unit , and very capable it is too.........The only down side to dcc that i can see is the cost of chipping loco's etc.
Hope this ramble helps...if you need to know more feel free to p.m me i'll try to help out.
regards..bob.
