Spiritual communion is a prayer one can pray if they can't receive communion at Mass and it's a good prayer to pray if you're making a visit to a tabernacle outside of Mass. Sacramental communion can be conferred in extraordinary circumstances outside of Mass, and I would think that the same graces conferred through reception of the Body and Blood of Christ during mass would be conferred outside of the Mass setting. (Is conferred the right word?)
But what graces are not conferred on the pray-er who asks for spiritual communion? Or, less specifically, what is found in sacramental communion, that is not found in spiritual communion?