I prefer Ubuntu in general, but one thing that Debian has really nailed is installation. Last week I installed Debian on an old machine using no removable media other than a corrupted Ubuntu installation CD.
Under Debian's hard disk booting installation method, you download two files (a kernel and a disk image) to your disk, which are under 6MB in total. Then you ask grub to boot the kernel with the specified disk image. There is enough magic in there to launch a Debian installer that downloads all the packages it needs from the internet.
All you need to do is get those two files onto the disk. Easy ways to do this include: booting from a liveCD (or another functioning OS on the disk) and downloading them, or ripping out the disk and connecting it to another computer. Unfortunately, I did not have a good OS on the disk, nor a working liveCD, nor a PATA dongle.
The disk I was using already had grub installed. The Ubuntu installation CD got as far as formatting the drive, but couldn't install any packages because they were all corrupted. Fortunately, there is a recovery shell which includes, among other things, wget. That was enough to get the ball rolling for a successful Debian install.