I am also prefer to work with steel studs for bench work construction. On top of the steel open framework I add a base of 2" extruded foam and use Woodland Scenics foam risers for sub-roadbed. I use foam struts to support old-fashioned chicken wire forms covered with plaster gauze for my scenery. I have a photo album on my website which illustrates my experience with this materials and techniques.
http://www.augustastationmaster.com/foam_steel_construct/
I'm completely satisfied with this construction method and would never go back to wood.
Hello,
I used furring strip on my first layout with some success. It is very hard to get straight furring strip lumber, therefore I used a solid plywood deck to straighten out the frame. Even with bracing, it is very hard to get the table stable, unless one end has been bolted into the wall. The other issue was splitting, eventually wherever you had connectors (screws or nails) you later developed cracks. For my last layout I have ripped plywood into strips and built the layout that way. It was a little more expensive but it is very stable and very forgiving.
I hope this helps.
Ray