Look up tables vs. value fields via combo box on form

I have tables such as t_WeatherData in which I have fields such as
Temperature, WindSpeed, WindDirection. The WindSpeed and WindDirection
fields each have a lookup table with an ID (primary key/autonumber) and a
field that holds a category ("N", "NE", "NW", "W", etc., or " 5 mph", "5-10
mph", etc.). As I have it, the look up tables merely serve to populate a
combo box on the data entry form...

OR, is creating a combo box with a value list sufficient?

What should be the factors in my decision on when to use a look up table vs.
value list in a combo box? I can think of one and that would be to use look
up tables for those situations where more values may be added... It seems to
me tables are just the all around solution because if you have to make any
changes, it's much easier in a table... ? But I am aware that caution must
be exercised because if a category is changed (made more refined/specific,
for example), then that will apply to all previously entered data because of
the ID... but then this brings me to my next question:

In the case of using lookup tables... What determines whether to use the ID
in the data table vs. just the category descriptor? To illustrate, I could
have my selection of "NE" in the combobox for WindDirection input the ID
associated with it into the field in t_WeatherData, or "NE" itself can go
into the field. What's best? Does it really matter?

Thank you, and these are my last questions for a while! I hope they were as
clear as mud. ;-)

Jill