Cab control wiring question

[tv_man]

I started wiring my layout with cab control to facilitate two trains running simultaneously. I have two controllers (DC) and all the track sections are supplied with dpdt switches, so I could isolate the sections on both sides and wire them with two wires running from each dpdt switch to the track but somewhere I remember reading, that it is enough to isolate only one track which would be connected to the dpdt switch while the other track (in all sections) would be connected to a common wire running back to the controllers. Apparently this would still work with two trains, but I figure it might have some problems which would make the fully separated sections preferable. Does anyone with experience with cab control have any opinions on this subject?

Hopefully this wasn't too confusing...