To claim that World War One was less brutal than World War Two is really a tough claim to back up. Both wars were incredibly harsh on all who participated. The most common and accurate generalization I've heard is that in WW1 it was really tough to be a soldier, in WW2 it was really rough to be a civilian.
On the Western front in WW2 the main development that was responsible for so many civilian casualties and poor living condition was the advent of strategic bombing. The problem of course being that aerial bombardment was not refined enough to allow targets to be destroyed without dropping thousands of bombs in the area. On the Eastern front though it was just sheer animosity.
That said if you were a German civilian in WW1 being blockaded for all those years wasn't exactly a walk in the park. Or in Britain after the opening of the Somme if you lived in one of the areas that the "Pals Battalions" were recruited from to open the newspaper and see the list of casualties included every man on the street you lived on, and nearly every man of working age you knew it must have been enough to make some people just snap.
As for being a soldier though if you gave me a choice between serving at Verdun or Stalingrad on either side I'd choose Stalingrad every time without thinking twice.