Whats the difference between a normal western saddle and a western saddle with an equestrian seat

If you mean an 'equitation' seat, the difference looks minor, but makes a big difference in the rider. Generally, an 'equitation' saddle is higher in the front part of the seat and thus forces the rider to sit in one position and not move around. The cantle has a tendency to be big and blocky, and the horn will be short and angled to the front. This saddle's main purpose is to help the rider stay in one position and look good on the horse, since equitation is judged on the rider's appearance on the horse. They are generally very comfortable to ride, but many riders like to be able to move around a bit more on the horse than these easily allow you to do. Many show saddles for western pleasure and rail events are of this type.

Western saddles have many other types of seats-- for example, a cutting saddle is made with a high, thin horn for good grip, and a seat that allows the rider to sit low on the horse and shift to find correct balance. A team-roping saddle is built on a very heavy-duty tree and usually has a deep seat, upright horn, and medium-height cantle. A calf roping/tie down roping saddle will usually have a low cantle to aid in the rider dismounting quickly, with a deep seat that sits the rider a shade farther back on the horse to aid in balance and a fast dismount. A reining saddle fits low on the horse with a deep seat for security. A barrel racing saddle usually has a high cantle, short, deep seat, and tall pommel to lock the rider in place during the quick turns and fast pace of a barrel race. An all-around, or ranch saddle will generally have a deeper seat with a low or medium cantle, a roping horn and pommel, and possibly bucking rolls depending on the tree style with heavy-duty construction. A trail saddle will generally be constructed to look like a ranch/all around saddle, but will be made of much lighter material since it is not subjected to the conditions and forces of roping and heavy use.