I find that Western riders tend to ride more from the seat, I mean literally, the seat. Becuase the stirrups are longer, and because they spend more time IN the saddle, they use more seat influence. the rider will not be as able to 'feel' the horse through the saddle due to the heavier layers of material between you and the hrose, and the shape of the tree brings the rider a bit higher up off the hrose's back, too. the rider tends to keep their leg more off the sides of the horse, at least in the lower part of the leg, and does not ride with as much pressure from the calf on the belly.
English riders tend to ride a lot more off the leg. the strength of the leg and it's firm , cohesive contact with the horse's body, all the way down to mid calf, provides their 'seat' and their influence on the horse . They will feel more the sense of having the horse between the rein and their leg, Whereas the western rider must work more on just having a good , balanced seat, because they are not useing firm, constant leg contact to keep the horse 'on' the aids.
I love having the horse under my leg, and having the feeling that I have his body under my leg, and his mouth in my hand, and all of him in between. However, when I spend a few years riding Western, it helped me to relax more, drop more onto my seatbones, stop 'gripping' so much and ALLOW more movement of the hrose's head and neck and LET him make more decision on where he wanted to put his head and how he wanted to transition up or down in the gaits, etc.
People say the horn makes them feel more secure, but I find the way my legs hold on to the whole horse's barrel in an English or dressage saddle to be far more secure feeling than in a big Western saddle. Just my personal opinion, though