<p>Say I have a method that needs to pull 8 values from a map with 100 elements in it. Which do you think would be preferable:</p>

<p>Walk in a for loop from begin to end once, pulling the elements out by switching on the key?</p>

<p>Or using find 8 times to get those values?</p>

I would use find 8 times.  It will be less (and more obvious) code.
You should try not make performance judgements based on small numbers since (a) it isn't likely to be a performance bottleneck either way at this size and (b) the numbers may change in the future -- choose the algorithm with the best asymptotic performance.
Note: you mention 'switching' on the key ... that may apply in your case, but in general you can't switch on the key value in a map.  Allowing for this would make the code to searching for M items in a map by iteration even more complex.