One of the ways to add applications to your NAS is by running containers on the NAS itself. Both QNAP and Synology have user-friendly interfaces that allow you to create, manage, and run your containers. Synology calls this feature "Container Manager," while QNAP names it "Container Station."
These two solutions share more similarities than differences. Lets look at the little difference they have .
QNAP Supports LXD, Docker and Kata. Synology only Docker
Docker is the most popular container platform , yet it's not the only one . Thre are many other Alternatives notably LXC/LXD which allow complete OS execution as a container, and Kata which offers better isolation through VM . QNAP supports Docker, LXD, and Kata.
There are many articles that detail differences among these platforms, but it simplifies to this: If you require an entire OS like Ubuntu as a container, opt for LXD. For greater isolation beyond standard containers, select Kata runtime . for everything else, use Docker .
On QNAP you can use all these, while Synology's support is limited to Docker.
Synology Offers Granular control over runtime privileges, QNAP has only a privileged mode
Docker has a "privileged" mode, granting containers access to all host devices. Both QNAP and Synology let the user enable this privilege mode with a simple click . Synology goes a step further by supporting the 41 Linux capabilities, offering finer control over privileges.
List of all the Linux capability options Synology Supports.
QNAP lets you access container volumes from host easily, Synology Doesnt
QNAP offers the flexibility of mapping volumes both from the host to the container and vice versa. However, with Synology, you can only mount a host volume to a container. This means that if you need to make changes to container files, QNAP provides a more convenient option.
Here is TL;DR of the entire article
QNAP supports Docker, LXD, and Kata runtime, whereas Synology only supports Docker. This translates to quicker performance for full Linux OS on QNAP and more secure, isolated containers compared to standard Docker containers on Synology.
QNAP supports only privileged mode, while Synology offers finer control through Linux capability options , in addition to privileged mode
QNAP supports container volume mapping to the host, useful for modifying configuration files within the container for example.