I would say that neither of these bags is particularly shoulder friendly, unfortunately (I have owned several MABs and MAMs in the past). The solution with the MAB is to get a matching shoulder strap, but to my knowledge a matching shoulder strap was never produced for the yellow/silverspot MAB - and I have never seen one on either ick-bay or the Bonz.
You might also want to take into account the fact that there have been a lot of quality control issues with RM bags (some more than others), and the bags with signature hardware (like the exact MAB you are interested in) have been particularly problematic. Not
all of them - but certainly enough of them to be worrisome. If you take a look at the "Quality Control/Customer Service" thread in the RM main sub-forum, you will see that sending a bag in to RM to have it fixed is generally not a picnic, either. (I also speak from experience on that point).
Sorry to be the bearer of bad news, but I would hate for you to be disappointed in your purchase.