The 700 comes chambered in short action cartridges, long actions cartridges and long magnum cartridges. The barrel lengths are typically 24 or 26 inches long depending on if it is chambered for a standard or magnum cartridge.
The seven is a short action rifle only and the rear bridge of the receiver is shorter than it is on the 700 by about a half inch to make an even more compact rifle than the short action 700. Barrel lengths on the seven are typically 20 or 22 (short magnums) inches long. The seven has a smaller barrel profile than the 700 does and they weigh about a pound less than the 700 does. If I'm not mistaken the seven's length of pull is shorter than it is on the 700 also. Basically the seven is more of a light weight, compact "mountain" rifle.