The two 16 ohm speakers are most likely in parallel, yielding a power handling capability of 4 watts at 8 ohms. Logically, assuming the capability to drive those speakers exists, the dual speaker rig would have better volume and sound quality.
Never heard of "Railsounds Lite", that's a new one on me. 
What are the exact Lionel numbers for those locomotives and where do you see the reference to "Railsounds Lite"?
