Turbines produce higher frequency noise where as piston engines are lower frequency. Given the same exposure to both at the same distance and volume, higher frequency noise will damage your ears quicker and be more annoying than lower frequencies will.

I've worked around turbines and recip's for going on thirty years and would rather listen to rap than any form of screaming turbine engine! that being said I love the concept of the turbine boats. I would love to see one.. but I would bring my ear protection.