The main competitor of the Drivestor 4 Pro is the Synology DS420j, which uses the same CPU and costs $30 less, but only comes with 1 GB of RAM while the Asustor has 2 GB. However, you cannot upgrade the RAM in the DS420j. The same goes for the AS3304T, which is a significant downside of both. On the other hand, its operating system, DiskStation Manager, is superior to Asustor Data Master (ADM). Not that ADM is mediocre, it is just that DSM is that good with its fresh upgrade to its seventh edition which introduced lots of new features along with many UI changes.

The server's CPU lacks an embedded GPU, so there is no HDMI port, which is a major downside for a multimedia-oriented NAS. I know that most of you prefer streaming to your devices, but a direct connection to a TV means you can enjoy super-high bit-rate files without stressing your home's network. Plex support is an advantage, but it is only for up to 1080p without any hardware transcoding, so the weak CPU will have a tough time. Media mode will help since it reserves 512 GB of memory for multimedia tasks, but ADM is more memory-hungry than DSM. If you try to transcode a 1080p file, the NAS will have a hard time, and you will most likely eventually lose patience. So stick to the original file format, not only with Plex but also with LooksGood, an Asustor application for playing and managing videos.

The 2.5 GbE port of the AS3304T over the similarly priced Synology DS420j without one clearly shows its advantages in multi-client scenarios under heavy throughput. CPU and RAM utilization are high in those scenarios, though. Basically, RAM utilization is reported as high even with the NAS at idle, so either ADM is memory hungry or its corresponding resource monitor is not working correctly. A stronger CPU would help achieve better performance with multiple clients, and it would also help with encrypted file transfers, where performance loss is notable. ADM is also to blame for this since the DS420j's encrypted network transfers are faster. I would also like to see better performance with external storage using the EXT4 file system.

Asustor paid extra attention to this product's exterior design since it is mainly for home use, where design matters as much as usability. It is also affordable but still more expensive than the DS420j. It has several advantages over the latter, with the most significant being the 2.5 GbE port, twice as much RAM, and expandability through its USB 3.0 ports. Don't expect high performance with expanded storage since USB 3.0 ports are not that fast, and the weak CPU will also set the limits. Why didn't they use a stronger CPU? Because it would notably increase cost and affect energy usage, and in NAS products meant for operation around the clock, every watt counts.