Coiba Island on the Pacific side can be reached by two operators out of Santa catalina: ScubaCoiba and Coiba Dive Center. It is also visited by the liveaboard Yemala. Coiba is known for big critters and somewhat difficult diving conditions (you should be fairly experienced).
Bocas del Toro offers very easy reef diving, depths average about 45 feet max, no current, and flat calm sea conditions on the inside reefs. Visibility averages about 40 feet, but can decline with heavy rainfall. The Smithsonian just did a survey of our reefs in Bocas and we have about 90 species of coral, 140 species of tropical fish, and about 200 species of non-coral invertebrates (sponge, crab, lobster, shrimp, octopus, squid, sea cucumber, etc.). If you can make it to Bocas in September or October (our slow season, but interestingly the best time of year to dive) you can access the outside reefs, where you can see bigger critters, caves, swim-throughs, pinnacles, etc.