Cooking with a crock pot - temp

Question

I'm thinking about getting a slow cooker, so I was checking out some recipes. Many say something along the lines of:

Cook Time
4 - 5 hours on LOW
2 - 2.5 hours on HIGH
Slow Cooker
4 - 4.5 Quarts
6 - 6.5 Quarts

Two questions:

1. Is it better to cook it on low or high? Obviously the time will be different, but will it usually taste better when done on low?

2. What is the stuff under Slow Cooker referring to?

Thanks

Answer 1

Cooking "Low and Slow" allows the heat to break down the connective tissues that cause toughness in meat, creating a more tender dish.

As for what the "Slow Cooker" is referring to, that is the volume of the crock pot.

Answer 2

For a pretty exhaustive list of why you would want to cook at a lower heat when time allows, see this question as most of the mechanics of letting your dish sit overnight apply when extending the cooking time by a few hours and lowering the temp.

In particular, I would look at this answer regarding passive transport; the difference being that you would be adding heat, further facilitating the listed mechanics