Well, I'd would prefer in some cases to stay with Ubuntu, mainly due to the fact that it is the only distro that will support my Laptop's video chipset, that being the ATI Radeon 9700 Mobility M11. However, if EnvyNG can somehow be included in future versions of OpenGEU in Debian, than I'll go debian. I don't really have any special preference, if Debian offers more stability than Ubuntu, then by all means - go Debian!
I'm also a little ticked with Ubuntu, primarily due to the changes in Karmic. One of the biggest things that really ticked me off was the new GDM. I can't use any of my GDMs I've collected on Gnome-Look! :-( And I loved the fact that I could randomly get a new logon screen at boot-up. That was simply WAY cool!
But now they did away with that! Big turn off for me. And the whole Xsplash thing? Is it really necessary? Just "eye-candy" for me...
My 2 cents worth...
Again, if it offers more stability, go Debian. Otherwise, stay with Ubuntu.