I have made the switch totally fairly recently. I ride in a 17 a/p, but a 16 seat in a western. I will say that I personally like the feel of a close contact (butterfly) skirt on a western saddle, as well as a narrow twist, and a deeper seat. Guess that makes me feel more like I would in an english saddle........lol, So, I ride in a reining saddle......just have more leg movement and contact, I think, but JMHO. I also do reining, but that is another subject.
THe biggest thing to get used to is the weight, obviously.
You will also need to try a few and figure out what fits your horse. Not only the bars and gullet measurement, but the length of the skirts on your horses back, since you don;t want them too long. Frankly I have found it much more complicated, but I am sure the western riders going english say the same thing!
Good luck! Have fun!