I like Dressage Today :3 but then again, im bias because I do Dressage, LOL
They don't have JUST huge upper level Dressage-y stuff in it. They have a lot of lower level stuff too, like articles on the importance of flexing your horse, counter canter, circles 101, posting effectively, etc.
I had no idea about the Practical Horseman, I always figured that was a Western Rider magazine, LOL.
Horse illustrated is good for a lot of the basic stuff too, so im glad you have it =) Horse and Rider is also good with basics, but they feature western as well ^_^