Debian is more logical if you are talking about building a platform because you already have to deal with very fluid FS code. If you also have a bleeding OS you will further complicate your world. I think ubuntu serves a good purpose to allow pre testing of what's coming down the pipe in a similar way to running the master branch of any one software. Just with ubuntu in many cases you are running the master branch of everything including the compiler and the libc and all the libs. I know there is a more hardened version of ubuntu that is more suitable for production but it really seems like its a more logical choice for a desktop OS.
Debian seems to do a good job of saying current. I personally use one of everything since I have to make sure it works everywhere =D