I'm in the midst of trying to compare them myself and trying to decide whether to keep the 2013. The 2012 isn't here right now, but I can measure the shoulder width on both tonight. I can tell you the 2012 is a lot less intrusive, even if it were the same width. The sides are smaller and don't extend as high. I like the protection of the new one, but the old one could be better for fitting someone next to it and them not feeling as claustrophobic.
On the surface, they look so similar, but the details are more different than I'd realized, based on what I'd read and been told by Britax when I called to ask specific questions. For example, I find the new shoulder belt guides to face more to the side, so it might have solved our challenge at that time, contrary to what the Britax rep told me leading me to not buy that seat. Also, they told me the width is the same. Yet when I tried the 2013 in the car/position in which the 2012 is very tight to buckle to the point of being difficult for an adult and impossible for a kid (because it's too wide at the rear against the buckle), the 2013 took no effort to buckle and I'm sure a kid could easily do it themselves. I didn't ask the rep about the width overall, but was very specific about the situation. Their reps are sure doing a good job of talking people out of buying their seat.
Where'd you find your cub pink? They're out everywhere I've looked.