PRINCE2 is a methodology that is primarily practiced in Europe. Unlike the PMBOK Guide which is a collection of best practices which empower the project manager to make decisions and use tools, the PRINCE2 methodology is far more prescriptive. Plus virtually anyone can be a certified practioner through training and taking an exam. There are additional trainings and qualifications to become an APM certified project manager (APM is a PMI-like organization).
A key differentiator of the PMP is that it requires real-life experience and not just training and/or a test.
But the bottom line is you need to look at your prospective employers and what they require. Most North American employers value the PMP more than PRINCE2.