Eric,
Damn, thats a big 6-yr old!
People say the EVS runs small, so an average size guy like me would want the XL, and a bigger guy like you might have an issue. The construction seems like it would offer a more "progressive" support, the Leatt more rigid.
Very good point about the Leatt pulling into the throat. Not common in MX but in the woods vines, briars, etc snag you regularly.
Likely the Leatt is better for a warp speed getoff, but for average woods speeds perhaps the EVS is good protection, and at the price more people will tend to buy one. Basially what concerns me with the Leatt is another broken clavicle, especially the right where there is the end of the plate and 3 screws near the sternum. There seems to be a high incedence of broken clavicles with the Leatt. Now, of course a broken clavicle is better than a broken neck, but can it be broken in a moderate crash that would otherwise not result in a neck injury without the brace? I guess only time and data will tell.