I don't know that one is better than the other, just different.
The X has a bigger screen, and more memory out of the box. But the Incredible has a more advanced screen (A little crisper/clearer), and is a good bit smaller overall. The Incredible also only has 10gb of memory, and is not capable of HDMI hookup.
They both have the same processor, and run the same OS(Droid) and apps. Even the differences in Cameras will be negated by a software download for the Incredible.
I liked the more memory, and bigger screen on the X, so that's the one I went with.