I think that the Droid X is an overall better device that the current Galaxy S versions, however, we will see how the Epic 4G is going to be.
I own both the Droid X and the AT&T Captivate. I like the Droid X more. The Samsung Galaxy S is a nice phone but the Droid X just offers me what I want more. The LED Notification Light on the X is a must have for me, the build on the X is better. I do like the size of the Galaxy better but overall I like the X better. IMHO After owning both phones, I would still buy the X over the Galaxy.