The ud3 and ud5 look alot like, the only main difference I see are the cap layout.
That and the slot config.
Otherwise it looks like the same board.

If they end up having the same bios, I'de go for the ud3.
It would be the one to compare to for the price.

I'm betting now there isn't much difference between them and the old generation.
After I've seen the 2 diff ud3's and the ud5, I think it's just a different layout from that of the 890fxa-ud5.
The 890fx didn't get the bios support for the new cpu's, and perhaps the ageis or whatever type of updates either that come along with continued support.
To put it short, newer board, it might clock a little better even on a thuban after it's been out long enough.

The only reason I think this board could be any better then the 890fx, is because of the bios updates.
And no hassle sli.
If you're still on the 790fx, or nvidia..., the 990fxa-ud3 looks like the way to go.

The ud5 kinda bugs me from a price point.
Shame they couldn't just get rid of the ud3 and price the ud5 starting @ $130.