I have the blue Aerborn ones and think they do the trick.
One of my lads legs swells up if he's in the stable and I put these on when he's in there and it certainly seems to help, still not entirely conviced what the magnets actually do for him. He's old and stiff horse and I've been doing lots to help him so couldn't pin point one thing as being it - if that makes sense
I've used the blue aerborn ones all winter and into spring, they're really good (don't move etc). the only thing I found was they're a bit warm, when we had a hot spell I wasn't using mine as his legs were going that horrible greasy too warm way and didn't want to risk any damage. Mind you within two days his windgally bits were up with a vengeance so reckon they must do something!
I have the Armadillo magnetic leg wraps, they are good and would recommend. You can also use them on all parts of the body as you can move the magnets about.
I have veredus magnetic stable wraps and i love them have used them for 3 full winters now and although i need to get some new inners before this winter they are in great condition and i love the fact they are nice and cosy ( still breathable) though the winter and keep Skyes clipped legs cosy.