What career do you want? If you want a career in public accounting, I think the CMA would be comparatively useless. If you want a career in private accounting, them the CMA has more value. It won't get you a job all by itself, but can be beneficial to getting one. I considered getting one when I lacked the experience to get the CPA, but ended up being able to get a job that qualified for the CPA experience, so was able to get the CPA sooner than the CMA, so went the CPA route. CMA renewal fees are more than the CPA (or at least in some states – my state's CPA renewal fees are less than the IMA's CMA renewal fees), so the CMA can be a more expensive credential to maintain, but not a significant difference.
Personally I think the time when the CMA costs more in CPE than it's worth is when you have both CPA and CMA. I'm sure that there are jobs for which having both is necessary or helpful, but for most accounting jobs, both is just wasted renewal fees. So, though I planned for awhile to get both, I ended up decided to stick with just the CPA since I got it first.
The CPA is more well-known than the CMA, but the CMA is more targeted at the private accounting industry. I think that a valid case could be made for getting either as a sole designation. If you were qualified for both, I'd lean towards the CPA since it is more well-known and has a lower experience requirements (1 year vs 2 years in management-geared roles which seems subject to interpretation), but since you're qualified to sit for the CMA exams and not for the CPA exams, I see no reason not to move forward with the CMA exams. If it will boost your resume and help you get a job, then it's worth every penny paid in renewal fees and CPE.
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