When I first got into 3D printing, I had just one printer and—like many others—I started out using OctoPrint.
However, since Octo has various shortcomings and stability issues, and the developer also attempted to impose some of her skewed ideologies on users, I quickly decided to move on from it.
So, I went looking for alternatives and found Repetier. It impressed me so much that it didn't take long for me to purchase the full version.
For me, the key factors were the ability to seamlessly integrate multiple printers, the fact that the server runs on (almost) any platform or OS, and an interface that is practically self-explanatory. MQTT support is another positive feature.
Even though not everything is perfect yet, it was a good decision in my view.