I think they taste different from other crabs. IMHO, their main attraction is one easy-to-eat ginormous claw chock full of flesh.
OT: They are also known as thunder crabs in Singapore.
http://www.wildsingapore.com/wildfac.../hardwicki.htm
It is also called the Thunder crab because of the mistaken belief that if the crab pinches you, only a clap of thunder will make it let go. This is of course untrue.