I have 4 years of experience with web application development.?
The option you have mentioned are quite different than each other, You may need to dig up to know both of them. While Business process management incline more towards your desire in Project Management, Microsoft Dynamics would need you to start from basics which may take a while. We are also in a mid years where DAX 2012 is getting stable while next version AX 7 was just launched and have tons of time (Probably couple of years) to settle down. Nonetheless, it has amazing future as well. And more and more companies adapting ERP, DAX is one of the best choices to plan the future. I would say it is more of a personal choice than it is based on what really is best in the market. I have had 5.5 years of amazing DAX journey & I feel more than blessed to be here. But being said that, if Id have interest in some other field, Id have chose that as well. Also 4 years is experience means you still have plenty of time to explore, enhance your skills to go right towards Project Management, so plan accordingly. All the best! P.S. I also suggest you plan some certifications, which also enhances your CV. I have 4 so far and still plans for more.