Reining is considered the Western form of Dressage, BUT it is not Dressage. Reiners are not Dressage horses in western tack. The way you go about training and riding a reiner is so different then how you ride and train a Dressage horse. The goal is the same, to achieve the highest level of harmony between horse and rider. But the tasks for which it was designed are completely different (Dressage = Military, Reining = Cowworking). Unless you have ridden a lot of western in the past (or unless you just really have a desire to go western) then I would not suggest going with Reining. Learning to ride western will almost be like learning to ride a horse all over again. If you REALLY want to learn to ride western, I'd say go for it. But I'll warn you that switching seats is not a walk in the park. I'm going to opposite direction, from Western to Dressage, but I'm doing that because Dressage is what I REALLY want to do.
I would suggest going with one of the Hunt Seat teams (either over fences or on the flats). This will be closer to what you are used to in the aspect that you won't have to change to a new seat.
In the end it's really up to you. Before you make your decision see if you can test out the different disciplines to see what you like best. Go around to different trainers and take one or two lessons in each discipline to see what you like. I know that seems kind of odd to take only a couple lessons with one trainer, but most trainers will understand what you are trying to accomplish and will be happy to work with you.
Last edited by Jubilee; 01-20-2009 at 08:58 AM.