English, because that's how I learned to ride. I just feel more comfortable in an english saddle. As for showing, I also like being judged on how well I can do something (as in Dressage [even though I don't do it] and hunters), rather than how fast (as in barrel racing, pole bending, etc...).
I did ride my horse in my boyfriend's western saddle yesterday, though, and her canter is much more comfortable in it than it is in my english one.
I'm also starting to rope, so I guess I'm going to have to get my own western saddle and start teaching my horse to neck rein now.