Straight for the same reason MacfromOK said. Years ago when I was big into sporter milsurp rifles I had just restocked a butchered 98K with a nice Fajen walnut stock when I got the chance to pick up a civilian sporting Mauser in 7.92. It had the European style stock. Firing them both you could feel the difference as the straight stock tried to push straight back more and the European tried to rise more. Not a big difference but you could feel it.