well it'd obviously be safer on the pavement, but you're not allowed to cycle on the pavement so that rules that out! I mean a lot of people will cycle on the pavement, but you have no right to be there, unless the pavement includes a cycle lane of course.
As a general rule, Offroad/countryside > Pavement > Road, if we're talking about safety. But this isn't always the case - a nice flat wide offroad trail is generally very safe, but when you've got a steep, rutted, bumpy descent through woodland, that's potentially lethal for an inexperienced rider.
Personally, I ride either off-road trails or on the road. The pavement is safer than the road, but if I cycled on the pavement it would take about 3 times as long to get anywhere (crossing roads, avoiding pedestrians etc.), so I may as well have walked.