i would assume that clone troopers would win against metro police, combine soldiers, prison guards, or combine elites in ground combat due to their training and their laser weapons while the combine use ballistic (or, bullets) weaponry, but that's only the combine overwatch (if i'm not mistaken)
clones could just use their rocket launchers (i'm not sure if they have any but) or their ships (no, not the big ones, talking about the ships you fly) to blow up hunter choppers, dropships, and gunships (if dropships are not truly invincible, anyways) as well as striders
either way, i suppose in some cases (or most cases), lasers > bullets
in the empire's case, the same thing. just sic the 501st on them and you're done, unless you use the generic stormtroopers, then you'll have a bit of a problem, unless they shoot well for this instance