The rail is much heavier than a Vala. The Rail doesn’t seem to be trying to play in the full power, but not full weight category as the Vala or the upcoming Norco Sight VLT CX among others.
The Trek looks heavy to me. 52+ lbs for a top of the line build with carbon rims. Compare that to 47 for a Santa Crus Vala. Granted the battery is 600 vs 800 but it's still lighter even with a range extender.