I should keep my mouth shut since I haven't heard either model, but let me mention a few things since its your first post. First, welcome! This forum is definitely a great place to learn, and it has helped me a lot during the past few years. Which brings me to my second point: musical tastes and preferences vary greatly here--even among people who have heard the same product. In your case, most of us have probably not heard both monitors (especially the Yammies since they're so new), so we'll generally lean in the direction we know. I do it all the time. By the way, I read a lot and have read great pro reviews of both monitors--more of the Dyns, maybe because they've been around longer.
Typically, when researching here, all I do is look for trends among responses to find which products seem to please the greatest number of people. That's easy to do for low-cost mics, which people buy a lot of, but can be much harder for more expensive items like higher-end monitors. Which brings me to my final point, a suggestion from my humble experience: if you can swing it, but both monitors and use them in your own studio space for a few days. Just make sure you can return one set, of course. When I've followed this approach myself, I've found that one product usually wins me over pretty quickly in the comfort of my own home--and it's not always the most recommended. Comparing three sets of monitors in my own home yielded an easy decision that I can live with for some years.
Again, welcome and good luck with your decision.
J.