Reputed = Generally supposed or considered (to be) but with some doubt;
considered to be something(based on hearsay or not sure)

1) The reputed father of the child.

2) Chandu chekavar is the reputed murderer of Aromal in the folk tales from Malabar.

More: The reputed mob leader, the reputed author of the article, the reputed owner, etc.

Reputable = having a ‘good’ reputation esp. for being honest and dependable

Always use reputable if it is a ‘good’ reputation.

1) Make sure you buy your used car from a reputable dealer
More: A reputable college, A reputable firm of builders, etc.