I would say that metering for a single value is less precise (yet faster) than to scan the scene for darkest and lightest areas that you want to have textures in them. Using a simple +2 compensation for snow may not always yield desired results. If you go that route you just leave out other values without attention. Also +2 compensation (Zone VII) should correspond to lightest grey values rather than bright whites (but that can vary). I think color negative films should be able to handle slightly higher placement like VIII or even IX (+3 to +4).