Speaking in general bottle neck rifle terms, it can be better to fill a case. Some people swear by it. Myself, I go with whatever powder charge gives me consistent velocities in the range I'm looking for. I'm also one of those guys who believe a 30-06 will never be a 300 win mag. The advantage of filling a case is more consistent ignition, ie. the powder can't shift away from the primer, hence better accuracy through more consistent velocities.
As for compressed loads, the same is true about powder shifting, although with compressing the charge, one is trying to get more powder, or powder of a different burn rate to attain higher velocities.
Overall, I've found accuracy is most effected by cartridge length (bullet seating) and proper firearms construction.
Ryan