To start off, the CCNA form of accreditation is different from the MCP form of accreditation because they are offered by different companies. The CCNA is offered by Cisco Systems and relates to Cisco networking products while MCP is offered by Microsoft and applies to Microsoft products only.
However, if you examine the background of many IT professionals out there, you may be surprised to find that they have both CCNA and MCP accreditation to their names. Does this mean you should do likewise?
It depends really on what you expect to be doing with your accreditations afterwards. There are some things you need to bear in mind when selecting accreditations to train for.
One, do your research about each accreditation first. Does the accreditation look like something you can use in your present line of work?
Second, do you think you could be promoted to a better position at your present employer, or move on to a higher rank at another employer if you achieve this form of accreditation?
Third, are you using any of the products of either company at present? Meaning, are you using Cisco networking products at work most of the time? Or has your employer successfully been implementing use of Microsoft products instead? The knowledge you have now may be useful to apply towards accreditation later on.
Fourth, do you have access to training in your preferred form of accreditation? Many people want to become working students because they still need to earn income, but find it difficult due to lack of time and access to resources. If you can secure distance learning options for the type of training you require, so much the better.
Fifth, look for exam guides that can help you plan an exam preparation program.
Sixth, take practice tests to gauge how much you know, how well you can apply that knowledge under real-world conditions, and how fast you work under time pressure.
Lastly, make sure the exam place is an accredited exam provider for that type of IT accreditation you are seeking.