I can understand. It's hard to learn to read the graphs. You have to learn to read each as it's own curve. That, and because they are different headphone brands, exact close comparisons don't typically tell the story. It's more of a general thing.
The M100s clearly have more bass emphasis because you can clearly see how they drop down above 200hz--the upper range of the midbass. Whereas the Momentums are more linear up to 1200 hz--into the midrange a ways. So if you know you want more bass, the M100s could be the way to go.
Pads can make a difference in sound. More often than not, I've found that what the pads do for some people did not do for me when I've tried pad changes (there sometimes seems to be a hype around pad changes). So I wouldn't make a purchase decision based on a pad change (except to more comfortable pads). More something later on once you buy a headphone you can try as an experiment that might or might not work out for you.
One other thing. Is there a good return policy on the M100s? Buying headphones based on user reviews on the Internet is like trying to choose whether or not to buy a painting without actually seeing it based on what other people have said. So many of us buy with the idea we are "demoing" and can return it if it's not right. I've probably returned close to half of the headphones I have purchased. I see it as a cost of finding the right headphones
BTW: I really liked the M100s when I heard them.