Be very cautious with an instrument made of cocobolo. It is a wood that can cause an alergic reaction much like poison ivy. It is in a class called sensitizers and with repeated contact you can break out in an itchy rash.
I don’t have any experience with cocobolo. I don’t work in any of the toxic woods (bad for my lungs). It is a very dense and heavy wood that is gorgeous in it’s grain and color so it should give a harp that has a darker and mellower sound. Some other soundboard woods to consider are; redwood, poplar, basswood and mahogany. While they are non-traditional woods they all give good response and each has it’s own set of plusses and minuses. I hope this didn’t further complicate your choice. Much of the info on soundboards is from my readings. The only ones that I have personal experience with are Sitka spruce, western cedar and poplar. The others I have never used in a harp.