The NCR is not the best choice. They're an overstretched, corrupt Republic that is sliding into oligarchy, and nothing you, the player, can do will change that. At best you've given them a huge tax pot to scoop every bottlecap out of and a big lake to drain for more irrigation. Victory at the dam won't make the NCR suddenly see the light, they'll get more cocky, more gung-ho, more taxing, more expansive.
House however offers 1) the survival of the NCR, if beaten/pushed back, 2) technological progress, 3) a free city, 4) autonomy for local settlements, 5) crippling of the legion, and 6) robotic escorts.
The Legion doesn't offer much, true; and Anarchism does not automatically equal death nice bias you got there - if you work for it, you can leave the Mojave stronger than its ever been, a valley of free settlements and a Vegas at your control to direct as a free city.