There are several desirable qualities one should strive for when considering the design of units. These qualities are often contradictory and we can evaluate a unit in terms of those it does satisfy. In my opinion, these are the most valuable properties a unit can have:
A unit that is natural arises directly from our understanding of nature. In order to be considered natural, a unit must reduce the complexity of the physical constants when they are considered with the unit as part of the basis. An example of a natural unit is the charge of a single electron, or the charge of a single quark. Examples of non-natural unit are pH mol and meter.
A unit that is anthropic corresponds directly to a low-variation fact of human life that is directly intuitive to the human imagination. An example of an anthropic unit is the day. An example of a non-anthropic unit is the meter, since Earth's radius is not a direct part of the human experience.
A primal unit is an anthropic unit that is in some sense the most directly related to human experience. A unit of this type is normally a reference point that cuts across all human cultures with little variation. Of all the distinctions I will draw here, this one is the least precise. Regardless, I feel it is an important goal to find the primal unit when designing anthropic units. A perfect example of a primal unit is human body temperature, for things are classified as "cold" and "hot" in reference to it. A non-example would be the boiling point of water (or in the case of centigrade, some fraction of it, but see 'simple' below).
A unit that is ratio produces a meaningful result when two values in that unit can be directly and meaningfully divided. An example of a ratio unit is the Kelvin. A non-example is Celsius.
A simple unit lacks arbitrary complexity such as named subdivisions, named supersets, extra ratios between subdivisions, and various caveats. By this I do not mean something like the SI prefixes, which do not belong directly to any one unit. Joules are a simple unit, whereas centigrade, which introduces a hundred gradations needlessly, is not.
Taking these metrics in hand, any unit can be directly scored and compared to those measuring the same dimension. While not perfect, this score provides a good qualitative comparison of the various units.
Lets look at a few units. Sometimes I propose a new unit. I have not presumed to name these and perhaps some already exist and I am merely ignorant of them. These I give shorthand names. For example, artime would be an instance of one possible anthropic ratio time. The others should follow in a similar and hopefully obvious vein.
|foot||0||0||0||1||0||1||non-simple subdivision inch|
|meter||0||0||0||1||1||2||non-simple usage cm|
|arlength||0||1||1||1||1||4||average human height|
|nrtemp||1||0||0||1||1||3||absolute hot, absolute zero|
|artemp||0||1||1||1||1||4||body temp, absolute zero|