I have used Debian/Ubuntu Linux® distribution for at least 5years above. I sometime tried to use other Linux distribution such as Fedora, OpenSUSE, or CentOS ; however, I was not able to get used to them in my case. There are several reasons "WHY" I did not get used to other Linux distribution.
I have confused about how to install software. If someone uses Debian/Ubuntu Linux distribution, they can use and apt command on Terminal. I think it is understandable and easy to use software installation on Debian/Ubuntu. When I began to use Ubuntu, I did not confuse about confuse software installation. On the other hand, other Linux distribution is difficult to understand how to install software. For example, I tried to use yum, rpm, or zypper command on Terminal, but error message appeared on it. My feel was questionable at that time. It was like "Why it is not same way ?". I have search a lot about how to use yum command, but it was difficult to understand how to do. You know what this is talking about "Package Manager" on Linux desktop. In my opinion, I recommend to use DEB package for beginner Linux desktop users because it is understand to use command on Terminal.
There are software installation utilities. For example, if someone knows software name, they can search it on software installation utility such as Synaptic Package Manager. Of course, it is also search it on GNOME software. On the other hand, if someone does not know software name, how do they find it ? Beginner Linux desktop users should search about it each time. It is annoying thing. Thus, I recommend to software installation utilities. Each software is depending on someone's purpose. For instance, if someone knows software name such as GIMP, they can use Synaptic Package Manager is the best; however, if they don't, they can use GNOME software is the best.
Finally, .deb file is better to understandable installation software for beginner Linux desktop users. For example, if someone want to install Atom editor, there are several ways to install their machine.
In my opinion, it depends on favorite installation, but I recommend to use .deb File for beginner Linux Desktop users. It is easy to use .deb File on their machine after they should install GDebi Package Installer. Some software need dependencies software, so it is automatically that their searching and finding is better. Thus, I recommend it for beginners.
In conclusion, I know that it's up to someone's favorite Linux distribution is the best. However, I recommend Debina/Ubuntu Linux distribution is useful and understandable Linux desktop for beginner Linux desktop users.