I have both the Incredible and the X, though I deactivated the Incredible to activate the X so can't do a side-by-side comparison.
I am afraid I have to agree with most of what MSTICLARU described.
I also believe that the photos on the Incredible are better in terms of sharpness than that of the X. Whether that is due to more in-camera processing or not, I do not know, but the delivered product from the Incredible is much sharper.
In support of the X, though, call quality is leaps and bounds much better than the Incredible, the MotoDROID, my LG Versa and a host of others.
In addition, the X supports voice dialing via my Jawbone BT headset out of the box.
These last two - call quality and BT voice dialing support - are the primary reasons I am still debating which I keep and which I sell/return.