Do any of you find that cakes (and especially cupcakes) baked with all butter come out dry compared to those that use oil or butter/oil combination?

I've been playing around with vanilla cake recipes lately and have tried Billy's from Billy's Bakery in NYC, Magnolia Bakery in NYC, and Joy of Baking. They all use butter/no oil and come out too dry for my liking.

I will watch this thread with interest. I love the taste of butter in cakes, but sometimes they do come out a little drier than I would like. I use an oil-based recipe for my chocolate cake, which is amazingly moist, but I can't imagine it translating well into a vanilla cake...

Tubbs, same with my chocolate cake. It's oil-based, tastes delicious, and is perfectly moist but not too dense like a brownie. It gets RAVE reviews! The vanilla recipes I've tried lately (mentioned) have a delicious flavor, but come out dry.

I have an oil-based vanilla recipe that has the texture I want, but I'm looking for something with more butter flavor. I've tried adding butter flavoring to my oil-based recipe, but it tastes fake. I could go broke trying to find/create the perfect vanilla recipe!

Technically oil doesn't provide moisture to cakes but it provides, what we call moistness, which is the sensation how something feels in your mouth. You could try to reduce the flour amount a little bit in your all butter cakes. I always weigh my ingredients to make sure I get consistent result. There is a big difference in weight between 1 cup sifted, lightly scooped or dip and sweep method flour, the same recipe measured with these 3 methods will give you totally different results. If you happy with your oil based cake, you could try to reduce the oil and replace it with part butter in your recipe.
Or you could try replacing the milk with half and half or use milk and cream instead of just milk.