Interesting post OP! I was toggling back and forth for a while, trying to decide which one to tackle. Finally decided on the CMA last year, because I am currently in a manufacturing role that is a hybrid finance/cost accounting position and I realized I knew very little about cost accounting. Wanted knowledge + respect that comes with the CMA in a cost accounting function.
As for why I am now pursuing my CPA, I just don't think the CMA is good enough for what I want to do in the future. It's a great certification to have (sort of a specialty certification in my mind) and if somebody told me they wanted to go no further than say, finance or cost accounting manager in a manufacturing setting, I would say that's all you would ever need. I, however, plan to progress in my career a little bit further. I'm pushing to be a director of finance, but unfortunately for me, even though I have TONS of finance/FP&A experience, and some accounting experience, most companies want you to have a CPA if you oversee an accounting function (even if you have a controller level working underneath you).
I guess more or less, you could say I got my CMA for now, but getting my CPA for the future.
I think getting both has it's merrits, but agree with poster above; only manufacturing tends to consider it on the same level of the CPA. All other industries will be curious about it, ask you questions about it in an interview, and it may help you stand out some, but it won't necessarily give you a huge edge.