what is the difference between the 1 vs 10 degree spot view finder?
Besides the obvious answer of "9 degrees" , a narrower angle of measurement (1 degree) will allow less surrounding material around the spot being measured to influence exposure. This is particularly helpful with off camera reflected measurements when a telephoto lens is used, as the lens narrows the angle seen through the viewfinder, the exposure meter does not have the same capability , usually measuring a relatively wide 30 degrees, or so (depending on model). The narrower spot view allows simulating the narrowed angle of view of the telephoto, so exposure is more confined to an area(s) of interest. A 10 degree spot is less precise, so will take in a larger angle for measurement, but more selective than no spot reading at all, which will take an average of all reflected light within the measuring range of the meter. Narrower view angles advantages are not limited to telephoto use, they can be selectve in normal angle usage also by the ability to isolate a tone you want to use for measurement for a macro (close-up) shot, or even a normal angle shot needing a certain tone measured where the "shoe leather" method won't work (i.e. walk up to the subject and measure it at close range), like maybe in a zoo where the cage bars (thankfully) are in the way.