I've taken live crab home on ice, 2-1/2 hour drive from the launch, and cleaned them at the launch tossed the leg clusters on ice and cooked them soon as I get home.
I tell you I can't tell any difference in the taste or apparent quality of the cooked crab.
The main advantage of cleaning them at the stations provided by the launch ramp, to me anyway, is that I don't have to contend with the mess at home.
While cooking them at the launch parking area sounds great and I do have the gear to do so, after the crab are done you still have the drive home and I really don't like night driving if I can avoid it.