Tap water is cheaper and more envirnomentally friendly.
Bottled water isnt nearly as safe as it is made out to be. In fact, muncipal tap water is usually much safer because it faces much tougher standards and quality control tests. Well water now that might be a different story.
A teacher I work with uses the following case study in an environmental studies class at our school.
http://www.sciencecases.org/bottled_...tled_water.asp
http://www.sciencecases.org/bottled_...led_water2.asp (Part II)
Part II is filled with facts.
Now I'm not saying dont drink bottled water.......Relatively speaking it probably is much healthier for you than say drinking a bottle of coke. And it is often convienent for car trips.
And for a snake I always use tap water.