It seems more than a little strange to be comparing Dickson's Childe Cycle stories to Drake's tales of the Slammers; aside from the subject matter, the two series have very little in common. The Childe Cycle has an overarching story arc that was intended to reach from the 14th century into the the mid-24th, one that deals with the evolution of man into what Dickson referred to as Responsible Man, a fusion of the best traits of the Dorsai, the Exotics, and the Friendlies. In contrast, the Slammerverse is very much a Crapsack World, and nobody with any sense would regard the Slammers as being heroic archetypes in any sense. They're simply the best at what they do.
That having been said, given the conduct in combat of the Dorsai and the Slammers as described in the respective stories - do we really have any basis for regarding one group as being any better, morally speaking, than the other? We can leave the Slammers' Major Steuben out of this; it's made explicit from the beginning ("But Loyal to His Own") that he's a sociopath who enjoys killing. And pretty things. :)