I like the big "button" switcher (second one). It is easier to find in dark and to hit it. It has strong design. Really I know one rule that should be applied to electrical devices like this one (switcher), I heard it from my teacher in school:
The switcher should be in UP position - switched ON
and should be in DOWN position - switched OFF.
It is a law according to accident prevention. If a person switched switcher ON and (s)he was hit by electricity, (s)he would fallen down and pushed the switcher to switch it OFF. I think it is a historical story :), but you can see this rule is applied in 90% more cases, I think.