To be honest, I don't truly know that answer at this point. Perhaps, I haven't fully thought it out. Each has its own great features.
EFX photographs better because it doesn't have the glare of the metal and clearcoating, which is what we also see on-screen in some scenes in the Avengers and Captain America The Winter Soldier movies. The leather straps are really nice. The accuracy and size of the star. Limited edition of 1500 shields worldwide.
King Arts is a real metal shield (i.e. fully front and back). It's got that nice metal clink or twang sound to it. Since you guys asked for the knock video, every time I walk by it, I have to knock on it with my knuckles to remind myself of the nice metal sound. I fully blame you guys for this
. But it is not as accurate as the EFX and the straps are cheap. The star is noticeably smaller but better detailed. But even though the shield is thinner than the EFX, it is heavier due to it being fully metallic.
Just from seeing photos of the various shields on the internet, at this point, I think I would have to say the Chris Fields shield may be my all-time favorite. High accuracy metallic shield at its finest. Too bad I haven't started this hobby collecting when he was making these shields and completely missed out these runs before Marvel stepped in with their legal action.
So I don't know if my thoughts of these 2 shields will help you in any way because I like both in their own ways. Personally I would typically prefer the metal shield over the non-metal. But the accuracy thing also plays a pivotal role in me deciding. Neither shield is perfect. Both are close and better in different ways. If you are debating between which is better to get if you are restricted at purchasing only one of them, then it will all depend on your own personal preference. To me, it is still a toss up. The Lager shield also has a nice front finish, but I can't remember of the back resin material is true to the movie or not. If Cap's shield was a full piece of vibranium prototype shield from Howard Stark's lab, and all he did was paint the outside red and blue, then the back of the shield would still be bare vibranium, in which case the Lager shield should not have a resin material on the back of the shield. Sorry my inner geek is speaking outloud