If you want the rose petals to function as decoration for an event like a wedding, freeze-dried petals are best. They can be used for decorating a wedding aisle, since they are less slippery than fresh petals. If the rose petals will serve as slightly fragrant decor, or you want to make decorations that include dry or wilted rose petals, fresh rose petals will look great sprinkled in a gift bag, or added with dried flowers and rose oil to make potpourri.
Freeze-dried petals last longer, so the bold color and shape maintenance of the petals is best for adorning the tables for a reception or dinner party, since the petals are preserved for hours, even days. Fresh rose petals will wilt very soon, so are best used for things like decorating the bedroom for Valentine's Day, or can be added to the fireplace to give the room a pleasant scent.
Fresh rose petals tend to be more expensive than the freeze-dried variety, since the petals have to be plucked from the flower hours or minutes before the petals are used, which makes for additional labor. For this reason, freeze-dried petals may be best for larger decorating jobs.