The 7mag generally shoots heavier higher BC bullets faster, hits harder, blows less in the wind. It is also more expensive to shoot, recoils more and gets fewer shots before the barrel is worn. A little too much gun for tactical matches but it'll work. If you will be shooting ELR distances often it's a better choice than 6.5 Creed.
6.5 Creed offers less performance but is more practical for general long distance shooting.
6.5 Saum is a great cartridge! Real happy with mine. Mine sends a 140 hybrid at 3125fps which is a mild to medium load in my longer barrel.