This might be a bit late, and may not be completely correct, but I think the major difference is the tone. まったく generally has a negative tone, and is more of "at all" while すこしも seems to be a bit less negative. The majority of the examples use "a little bit" in the translation and can also be used in a positive sense. The third example uses it in a positive way, while I've never heard まったく in any way except negative.
While they both mean "not at all," 少しも~ない is more polite than using まったく, and the latter almost has a sense of hopelessness - like if you said 日本語はまったく話しません, it has a feeling of "I don't speak any Japanese at all (so there's no use trying), whereas 少しも is more neutral and doesn't have that nuance.
