Below is an excerpt of an answer Erik Hamburger of Ambidexter Management answered on LinkedIn. Click here for the full question and all the answers.
The primary reason for Prince2 was that at that time (1997) it had just emerged from the UK into the Netherlands and it seemed (and proved) to be a very powerful process driven PM methodology. I has studied the PMI PMBoK at that time and found (and still do) that more descriptive and Prince2 more prescriptive.
PMBoK and Prince2 can and should be used in conjunction. More about PMI a bit later.
Since I had done Prince2 it was only natural to do MSP (managing Successful Programmes).
IPMA (International Project Management Association) is more competence based as opposed to PMI's knowledge focus.
Now that I live in North America a PMP almost seems a no-brainer. And in a way that's too bad. There is a lot of misconception about PM certification in general and PMI's PMP specifically. It is in no way a guarantee for success. You can get your PMP without ever having fully managed a complete project end to end. The same goes for the Prince2 practioner certificate. At least Prince partially prescribes you the way to manage a project and with IPMA B you have to have done a full project and give ample proof (both writen and oral) during the certification process.
When pursuing a PM diploma/certification ask your self the following question:
"What do you want to achieve with it?"
Get that job? Improve your skills? Get that raise? Because everyone does it? Being part of a community? Being a scholar?
Please note that there are countless PM training/learning possibilities out there that not all lead to a certification but do increase your knowledge and skill set that will be beneficial in managing projects successful.
I would like to point out that there is also quite a bit of misconception about Prince2. The most commonly criticism is that it is document heavy and can be overkill. Nothing is further from the truth. It is true that the Prince2 manual contains a full set of project document outlines. But as with any tool/template it is the application that creates the overkill or the right mix. One can manage a project utilizing Prince2 without tons of lengthy documents as long as the key concepts are adhered to. Key to Prince2 are the combination of the process model, the components and the techniques. (In 2009 a revised manual was released)