There might be an inaccuracy in my recollection because I have not been using Debian since 2006.
The shell scripts that run when the OS boots (in /etc/init.d/ and /etc/rc* IIRC) are a lot more numerous on Debian than on Arch -- or so I seem to recall. So for example I remember that trying to increase my boot speed by identifying and disabling unneeded services was an exercise in frustration. I configured my Arch Linux to boot to the text-mode console, and if I wanted to start X and Gnome, I used startx. I probably never tried to do the same thing in Debian, but am left with the distinct impression that it would have been harder. (Why would I want to do that? As a procrastination-reduction measure: when I wanted to focus on work, I would quit Gnome and X. On my slow machine, it would take a good 30 seconds or more for Gnome to restart, and the thing about procrastination -- at least for me -- is that if I can arrange it so that the decision to procrastinate is not immediately rewarding, then the temptation to procrastinate becomes weaker. I realize most people do not need their Linux install to help them fight procrastination, but this is an example of my tailoring my install to my particular needs, so I think it is relevant to whether Debian or Arch is easier to customize.)
When you build something from source on Arch, it takes very little additional effort to arrange it so that Pacman can install it and the arch build system can rebuild it from source. And if you make the effort, it becomes easy at a later date to look up what you did to get the software to compile, so the (again, mild) additional effort ends up saving you time in the long run when you need to rebuild stuff you built years ago. And since pacman installed every file in my /usr and my /bin, if I ever needed to know where a file in /usr or /bin came from, pacman was able to tell me even if I had compiled the software from source. I know that all this is doable on Debian, but doing it on Arch is very very easy. So I liked building stuff from source on Arch better.
The shell scripts that run when the OS boots (in /etc/init.d/ and /etc/rc* IIRC) are a lot more numerous on Debian than on Arch -- or so I seem to recall. So for example I remember that trying to increase my boot speed by identifying and disabling unneeded services was an exercise in frustration. I configured my Arch Linux to boot to the text-mode console, and if I wanted to start X and Gnome, I used startx. I probably never tried to do the same thing in Debian, but am left with the distinct impression that it would have been harder. (Why would I want to do that? As a procrastination-reduction measure: when I wanted to focus on work, I would quit Gnome and X. On my slow machine, it would take a good 30 seconds or more for Gnome to restart, and the thing about procrastination -- at least for me -- is that if I can arrange it so that the decision to procrastinate is not immediately rewarding, then the temptation to procrastinate becomes weaker. I realize most people do not need their Linux install to help them fight procrastination, but this is an example of my tailoring my install to my particular needs, so I think it is relevant to whether Debian or Arch is easier to customize.)
When you build something from source on Arch, it takes very little additional effort to arrange it so that Pacman can install it and the arch build system can rebuild it from source. And if you make the effort, it becomes easy at a later date to look up what you did to get the software to compile, so the (again, mild) additional effort ends up saving you time in the long run when you need to rebuild stuff you built years ago. And since pacman installed every file in my /usr and my /bin, if I ever needed to know where a file in /usr or /bin came from, pacman was able to tell me even if I had compiled the software from source. I know that all this is doable on Debian, but doing it on Arch is very very easy. So I liked building stuff from source on Arch better.