The fox is a chineese clone of the youngs and is a bigger dia at 5" ,where as the super lightweight /bob james lightweight from youngs comes as 4" or 4½" options,but thats all there is in it ,it all comes down too size and build quality .youngs has a good track record on build quality .but i don't think the fox as been around long enough too judge ,or theres not been nothing reported about them being poorly built .
if you can hold a cd/dvd in your fingertips comfortably by its rim ,then get the fox ,if not then get the youngs