DX Pros:
Camera Button
Gingerbread available now
"Better" screen (accurate colors, no ghosting, non-pentile)
More usable internal storage for apps (~6.x Gb)
Faster stock gallery
More active user community/3rd party support
Tiny bit better battery life
Smoother video capture when writing to an SD card than DX2
DX2 Pros:
Tegra2 performance
HDMI mirroring
Faster camera response
Louder earpiece/speaker volume
4Gb internal user storage partition
"Better screen" (higher resolution, brighter backlight, betterr blacks)
DX2 is more likely to see a future update to Ice Cream than DX
720p video recording has a max of 30fps (vs 24fps on DX)
DX2 has anti-glare coating on screen