Koha developer community recommends Debian Linux. Because they build Koha-Debian combo in their mind. Debian available with bare LXDE and XFCE desktop. Debian package repository offers the full bunch of packages required for Koha installation.
In the first phase, I downloaded Debian 8 (codename 'Jessie'!!) LXDE CD image. The ISO file size is only 646 MB. I burned the Debian iso file in a USB pen drive (save a CD!). And plug in the pen drive to my Acer Netbook and restarted it. On the way, I changed the boot option to the USB flash drive. The first screen of the Debian installation appeared in charm. The user can either choose either text mode or GUI installation step. Netbook PC configuration is very low and I selected text mode installation steps. Text mode installation is faster than GUI, but you can't play with the mouse! If you are going to install Debian on a Laptop/Desktop with good configuration, choose GUI installation.
On the way, select language, keyboard etc. I jumped Partition hurdle successfully (be careful). Debian installation will ask to put a password for root user. Again need to create a normal user account with ID and password. The root user has the full power in Debian. Ubuntu disabled root user and has another mechanism called 'sudo' to do administrative tasks. If Internet connection available, the installation process will ask to connect with Debian repository and download new packages to install. It takes too much to finish the installation; humbly deny the request to connect to the repository. After the installation, the system has to restart and we can enter into the slim and clean Debian XFCE desktop. You can experience the speed of Debian while booting.
Update of Linux is necessary after the installation. We need to add some extra Debian sources list to the installation. This website will help you for the purpose, https://debgen.simplylinux.ch/.
Ubuntu users addicted to 'sudo su' tool. The user has to install the sudo package in Debian and make available it. Debian user will get the administrative power with the command 'su'. Ubuntu user can easily win Debian Linux after the installation of 'sudo'.
Koha installation process in Debian is more or less same as in Ubuntu. You can follow the installation manual in Koha Wiki. Koha has some advantages with Debian. Plack now works well only with Debian. Plack is a speed booster.
In my experience, Debian is fast compared with Ubuntu and more suitable for Koha. Slim desktops of XFCE and LXDE with Debian can give the good performance.