If you find a good dry food I'd like to know too. I have two long haired cats and give them both Royal Canin Persian Dry and Eagle Pack Holistic canned.
As for the Royal Canin, I've seen some posts here on the forum that it's not a good food. Why I wonder? Because of the corn content in it? I like it because of the fibre added to help control the hairballs (and my older cat has constipation too). I bought the holistic dry food from Loblaws. They eat some of it but don't like it as much as Royal Canin. However, it doen't have any fibre stuff in it. With Royal Canin Dry I noticed the first ingredient is Chicken but for the Holistic Blend stuff the first ingredient is Chicken meal. I would think the one that has chicken as the first ingredient would be better regardless of having corn it it. BTW, none of my cats seem to be bothered by the corn.