I think the decision should really come down to which size you prefer. The Incredible is a fast and smooth phone with a beautiful 3.7" screen. Some people love the Sense UI, some hate it. The X has a bigger 4.3" screen and no Sense UI. It is using some sort of "Moto Blur lite" that is supposedly much less intrusive than previous versions and shouldn't slow down OTA updates. Battery life is supposedly not the Incredible's strong point while early reports say the X does fairly well in that department. So big vs small and Moto vs HTC. Either way, I'm sure you'll be happy.
Remember, no matter what phone you choose, it will be considered yesterday's news before you know it.