For such a major tourist spot, Bocas del Toro has surprisingly few tour operators. Nearly all offer the same popular day trip consisting of dolphin watching, sunbathing and snorkeling which has gotten good reviews. Prices are pretty uniform, but you may be able to bargain if you shop around. From what we've been able to gather, there's not a whole lot of difference when it comes to quality.
Michael Karanicolas is awesome.