I realize I'm late to this thread
but just wanted to weigh in.
I have five RM bags:
1) black MAM
2) cobalt MAB
3) seafoam mini Nikki
4) yellow mini Nikki
5) eggshell MAC
If I could only have one, I would choose the black MAM, without any hesitation at all. Here's why:
Size --The MAM is a great size. It holds everything that I need on a daily basis comfortably, but isn't
too big (the MAB is a bit large for my taste). The MAC isn't big enough for me to use as a day-to-day bag, though it's great for a knock-around weekend bag when I want to have my hands free.
Shape -- the MAM has a very classic, ladylike shape that dresses up or down easily. It's not what I would consider a "fancy" bag, so I wouldn't wear it with evening clothes, for example, but it looks refined with, say, a wrap dress and heels. However, because it slouches, it just as easily looks casual with jeans. The mini Nikki (and full-sized Nikki) have a much more casual shape, so they're less versatile IMO. I do wear my mini Nikkis with my suits, because I think that they give a fun pop of color; however, if I could only have one, I'd pick the bag with the more classic shape.
Leather -- Eggshell and Yellow aren't as nice feeling as Black, Cobalt, and Seafoam. All of the colors you listed fall into the latter category (soft and smooshy), I think, so that's not really an issue for you
.
Just my $0.02. I like all of my bags, but if I had to narrow down to just one, I'd keep the black MAM (and if I could only keep two, it would be the black MAM and the seafoam MN).
I'm sure whatever you pick will be terrific! Just make sure you pick something that goes well with your wardrobe and your lifestyle.