I selected the al-Turayyā Project and the Atlas of Early Printing for my study and comparison of mapping projects.
The al-Turayyā Project
The al-Turayyā Project is described by the archive as “Mapping the Arabic world in the classical epoque (circa 9th and 10th centuries A.D.).” Sadly, the Arabic world seems to be missing a few pieces, as can be seen below.

At first glance, I assumed that this was just an issue with the interactive map loading. Reloading the webpage several times, however, I discovered that this same set of tiles was consistently missing; I can only speculate as to why. The issue was, however, unique to the Google Satellite version of the map. The site also provides the options for Grayscale, Google Terrain, Water Color, and National Geographic versions of the map, the lattermost of which I used for the remainder of my time on the project.

Despite the initial issue with visibility, the technical features of the map seem to be in working order. The core of the project is the ability to click on a site or route (represented by the dots and lines) and find sources and other information on the topic.

Another item is its route-finding capability, allowing users to plot a course between two or more population centers and view the route, distance, and travel time that contemporary travelers would have likely experienced. I’ve used similar websites in the past for my own projects and found this feature incredibly useful for understanding timelines, particularly as far as communications are concerned.

The al-Turayyā Project seems like an excellent resource but is (to an extent) falling apart at the seams. Load times in particular are terribly slow or may require multiple attempts, leaving users unclear on whether the location they are researching has no data attached to it or simply is unable to load it. While potentially useful, I would consider the Project in its current state to be unreliable.
The Atlas of Early Printing
The Atlas of Early Printing is much the same concept as the al-Turayyā Project, allowing users to interact with a map of western Europe and click on points to view material regarding said point. This time, the key point are not population centers, but the arrival of printing at various places across the region.

Unlike the al-Turayyā Project, however, which had consistent technical problems throughout the time I used it, the Atlas of Early Printing had new and exciting technical problems each time I opened it. At different points I had all of the points disappear from the map when I attempted to zoom in, the map stick open at roughly the size of my thumbnail, and my entire browser crash when I dared to look too closely at Greece. All of these issues occurred only once and were fixed by reloading the site, however, so this seems a matter of instability.
Beyond technical issues, however, the map provides a remarkable degree of control to the user, allowing them to layer a wide variety of datasets beyond just printing on top of the map, such as bishoprics, universities, papers mills, trade routes, and more. The image below features the map with all optioned checked on, creating an incomprehensible mass which reflects (if nothing else) the number of options available.

The Atlas of Early Printing is a much more polished and user-friendly site than the al-Turayyā Project, although this may be influenced as much by the availability of data as the sites’ technical limitations. If one can overlook the instability issues, the Atlas could be picked up and used as is.