When it comes down to brutal pragamism the Lanius is better but only because he isn't emotionally invested in the conflict. New Vegas is Caeser's Rome not his. Lanius' real goal would be California as he basically states at the end of the Legion campaign. He isn't a smart as Caeser and I doubt that he'd be able to keep control of the whole of the Legion after the horrific loss of the Mojave Campaign. The death of the top members of the Legion can't be overstated and since the whole Dam operation was basically Centurations he'd be screwed. I do respect him since he knows when to stop but that's only in the face of defeat, facing the Courier. If he was true leader after Caeser's death he'd relize the Mojave was a death trap and retreat. It's not his campaign, nor his battle to fight, it's Caeser's from the grave.
I can understand gambling to take the Mojvae but after the desturction of Searchlight, Nipton and Nelson. The armed defense of Freeside, Westside, and Novac in which many die. And of course the massarces of Bitter Springs, Red Rock, The Strip, and Old Mormon Fort, who the hell is going to be part of there damn army anyway? The gecko's? In the end like Lanius said the Legion barely survived a situation like this in Denver which had few tribes and that he sees the same in the Mojave. Only this time the time field commanders are dead, the leader and founder is dead, many generals back east have there own goals for power and the largest nation on the planet is going to be back for revenge....not even the Legion could withstand.