CMA Scope

Both are good and I am not being diplomatic, I mean it. Syllabus coverage of both the courses is excellent and standard of questions asked in exams are also very good. If you are looking for starting a firm then CA has more scope then CMA for now but the scope for CMA for practice is also going to increase with GST coming into action. And for various relevant job purposes both the courses are given the same weightage in most of the cases. I know many people who are holding high level positions (related to finance etc) as a proud CMA in various government companies and Multinational Corporations. I also want to add that rumour of CMA being easy is totally false. Actually it can be said it is tougher because there are 8 papers in CMA Inter but only 7 papers in CA IPCC. One more point, there are no gaps between exams in case of CMA but in case of CA, students get one day for revision before each exam. Finally I want to conclude with saying both the courses are great in their own ways, you can go for anyone of them. Hard work together with proper strategy is the key for passing and success as well.

CMA vs CIMA: An Overview
The CMA qualification is granted by the Institute of Management Accountants and is also known as IMA. CIMA stands for Chartered Institute of Management Accountants, is a designation which comes from the UK.
Membership and Network
Both qualifications were conventional since a long time, but CIMA has a much superior presence with 218K members and students. IMA has around 70,000 members.
Global Presence
In terms of global presence, CIMA conventionally has a more global presence and is well familiar in most places less so in the US but more so in the UK and Commonwealth countries. In current years, the CMA (now CPA) Canada and CMA Australia are getting more widespread in their respective countries so CIMA is disputably less sought after in these countries.
On the other hand, IMA has been vigorously building up its universal presence, remarkably in developing countries e.g. China and the Middle East. For now, CMA is well established in China and is head-to-head with CIMA in the Middle East.
At the same time, CIMA pairs up with AICPA to establish a new qualification known as CGMA. CIMA members can pretty much pay to get the new designation before 2015.
Conclusion
There isn't a superior or simpler qualification. As fellow reader Gunner pointed out in the comment section, while CMA may look easier with only two parts in the exam, it needs a Bachelor degree, vs a high school diploma in CIMA. Or looking at it the other way, as CIMA has a lower entry barrier, it has a more comprehensive exam with extra papers and time/effort in the preparation.
A more important consideration is where you would like to work in a longer term. This will help you select the qualification best suited in that region.