Go to www.akc.org
and familiarize yourself with the breed standards. Also, www.kuvasz.com
has more information on kuvasz specifically. Generally, the kuvasz is a leaner, more active dog with a wavier coat and a wedgier head with a higher earset and more alert expression. The kuvasz has front dewclaws, but NO rear dewclaws. The pyr has double rear dew claws. Poorly bred kuvasz and poorly bred pyrs CAN nearly look alike. There was a time that kuvasz breeders bred dogs that were nearly identical to pyrs (heavier bodies and heads, long straight coat). Thankfully, those dogs are fewer and fewer in the show ring. The hungarian standard does not allow straight coats/domy heads so perhaps the US show kuvasz is starting to be more true to the hungarian standard.
The kuvasz standard does not mention "aloof". That is a trait many people use to excuse too shy dogs. The kuvasz standard says they should be suspicious and standing between you and any threat. Lively is also mentioned. A well socialized kuvasz can be outgoing and friendly in the show situation. One with too many fear issues will appear aloof and afraid.http://www.westminsterkennelclub.org
has videos of the breed winners from Westminster to show kuvasz and pyrs in action.