The major differences between the DS918+ and DS916+ are a newer CPU, more RAM, the two M.2 slots, and trays that feature locks on the newer model. Performance-wise, the DS918+ looks to be slower than its predecessor with real-life file transfers, which I can't explain since since both CPUs are of a similar capability. A change in DSM is probably responsible for this performance drop in real-life scenarios since the DS916+ was tested with a previous version of DSM installed. In the DiskSpd synthetic benchmark, though, the DS918+ takes the lead from the DS916+, and the same goes for the RAID sync and rebuild tests. Personally, I would like to see major performance differences between these models in favor of the DS918+. Given how the situation is right now, however, there is no reason to upgrade to the DS918+ if you already have the DS916+ unless you have plans on exploiting the two M.2 slots the latter provides.

With the DS918+, we have another Synology NAS that doesn't feature an HDMI port. It is simply a shame to keep this feature from users who want to connect their NAS to a TV or monitor. Streaming 4K content over a home network can prove challenging, especially if the NAS is simultaneously conducting other demanding tasks, which has most of us prefer an HDMI cable for our TV for our favorite movies and shows over Kodi since it completely eliminates having to worry about any bandwidth issues. The cost of adding an HDMI port is minimal, which means Synology should change its approach, especially since there are other NAS vendors with models that have even more than a single HDMI port, along with audio I/O ports.

The DS918+ offers good performance overall, although it isn't as high as I expected, compared to the DS916+ at least, though it is pretty quiet most of the time. Moreover, you can choose between the ext4 and Btrfs filesystems, with the first offering a little higher performance, while the second features enhanced data protection. The addition of the M.2 slots and the locks on the trays, which are still plastic, though, along with the increased amount of RAM, are nice improvements over the old model, and the fact that the price is exactly the same is appreciated as well. I should also mention the low operating temperatures of the HDDs with the DS918+ under even stressful conditions. However, I use low-capacity HDDs for my tests, and you should, as such, expect to run into higher temperatures with larger HDDs. Still, though, compared to other NAS servers I have evaluated in the past, the DS918+ runs its HDDs cooler, which is a big advantage. The DS918+ is a fine choice if you need a good and reliable NAS, don't mind the lack of an HDMI port, and your budget allows for it.