The biggest difference would appear to be that the McCanns were formally interviewed as official suspects while the other parents weren't. IMO, refusing to answer police questions did them no favours in the police's eyes and later in the eyes of the press and public.
from wiki..
Ben Needham was staying with his family on the Greek island of Kos,[8] where his maternal grandparents had a home in the village of Iraklis, near Kos town. He went missing on 24 July 1991.
On the day of his disappearance Ben had been left in the care of his grandparents while his mother went to work at a local hotel. Ben had been coming in and out of a farmhouse the family were renovating when, at approximately 2:30 pm, the adults realised he had disappeared.[9]
The family first searched the area for Ben, assuming he had wandered off, or that the boy's teenage uncle, Stephen, had taken him out on his moped. When no trace of the boy was found, the police were notified. They initially
questioned the Needhams, viewing them as suspects, which delayed notification of airports and docks.[10] Over the following 11 days, searches of the area were carried out by Hellenic Police, Hellenic Army and fire brigade personnel.[2] Nikolaos Dakouras, the island's chief of police, said: "We now believe we have searched every possible part of that area, and the boy is not there. It leaves us with a great mystery. We have no theories. We have no solutions."[11] Following a request from UK Prime Minister John Major, the Hellenic Army undertook further searches of the island in January 1993.[12]
