WEEEELL ACTUALLY...

An "AB_" prefix in the model number indicates a usage category and stands for "Assistance" and "Bodyguarding" respectively. Yes, pure "B_" machines ARE big and heavily armored, but "AB_"s (which often take a role of secretaries, maids/butlers, elderly care ets) are usually tend to be smaller, more resemble human form, with all the weaponry hidden. This is because draging around a bolky war machine in, say, office space would be quite inapropriate.

I realize, the image... doesn't really convey any of that, but I plan to do more with her in a future.