I've owned both. Currently, I'm on my third EZ P-51 in ten years. I have also been flying a WM Chipmunk for last last year. For those short on building time, these are in my opinion, the best two ARF manufacturers out there right now in the 40-60 size. Let me try to explain the differences.
For scale outlines, and overall quality of fit and finish, the EZ line of ARF's are amazing. I own the new all aluminum P-51. Pictures cannot do it justice. With just a little trim, I have duplicated "Wee Willie II" based nearby at Chino, CA. Every rivet, panel and line are done very well. The foam skin is very resilient and survives hanger rash better than film. All the EZ models I have flown have been fantastic. An old EZ P-51 powered with a .75 and 7 servo's was as easy to land as a low wing trainer.

Pro's... very scale, high quality, looks and flys great.
Cons...expensive, not easily repairable. Metric hardware.

My experience with World Models is equally favorable. They seem to be well built. I have never heard of a structural failure from World Models. I have tried. I installed a YS 1.20 on my Chipmunk and after more than a year of abuse, my Chipmunk looks and flies brand-new. The film covering is holding up better than expected. I have not had to do any repairs, but they would be easy if needed. There were no defects. The fiberglass cowl is a work of art and matched the film color perfectly. The flying qualities of my World Models Chipmunk are subjective due to the extra weight and power of mine. But I am very pleased with mine.

Pro's...absolutely the best value for the buck. I could not build this straight, light or cover a plane this well. World Models is like a very well built kit.

Con's...I'm struggling here. Marginal metric hardware. I replaced all with 4-40.

Since I won't use Metric hardware on any of my planes, I can't really comment. My experience with both of these ARF companies are favorable. Both filled the role for which they were purchased. Both have survived being overpowered without any structural problems.