totally personal preference. I recently ASSumed that my 9 year old daughter would want to ride western, because that's what I like. Nope. After afew lessons, it turns out that she loves english. She hates sitting the trot unless she is riding a reaaaaally smooth horse, and she likes to post. I hate posting.
Also depends on the horse available, at least for beginners. Kiddo is a beginner, and although the horse she has is well trained for western, he's young, and extremely difficult for a beginner to neck rein and slow down to a jog. He's much more cooperative for her direct reining and trotting out at this point. The horse also seems to prefer the english tack lol.