I've used both Atlas and ScaleTrax. Both have pros and cons. The biggest pro about Atlas is the tie length/width and spacing; the biggest con is that the flex is tricky (but not impossible) to work with. All new alignments at the club are being done with Atlas as it doesn't rust and is quieter than Gargraves due to solid rails.
ScaleTrax is easy to work with, but the joining is a bit tricky with the clips (not major). The tie dimensions and height are great, plus the rail height is nicer. The tie spacing however, matches concrete "commuter" trackage (as do the rail retainers) rather than wood. I had even thought about painting the ties off white to mimic concrete ties. When ballasted, ScaleTrax looks very good.
The big factor for you should be turnout and section availability. Atlas has more sizes available, plus it's easy to connect Ross turnouts to Atlas track. With ScaleTrax, you have to "trench" the Ross turnouts because the rails are higher and butt-joint the sections since no connectors would work reasonably well with the two track types. From a rail height perspective, I'd use Atlas track without cork roadbed and ScaleTrax with the roadbed.
Hope this helps some.
