Which is the most effective med amoxicillin or amox-clav?

Depends: Augmentin (amoxicillin and clavulanate) will be effective against all organisms that are susceptable to amoxicillin. It will also be active against some other bacteria that produce beta- lactamases which degrade Amoxicillin such as mssa and bacteroides species. If an infecting organism is sensitive to amoxicillin, like most beta-hemolytic streptococcus species, it would be the best choice for its more narrow spectrum and cost.