Performance - Product Comparison
The key question, of course, is whether you'll suffer a performance penalty in exchange for keeping $40 in your pocket. So I used the NAS Chart tools to run a comparison of the DNS-323 and 321 and threw in the top-performing (and significantly more expensive) Netgear ReadyNAS Duo.
Figures 15 and 16 show a comparison of non-RAID Write and Read throughput with a gigabit LAN connection. I didn't run jumbo frames plots because I don't have DNS-323 data in that mode.
Figure 15: Product comparison - 1000 Mbps Write
Writing, both the 323 and ReadyNAS have higher throughput at 32 and 64 MB filesizes. But the 321 cruises steadily along between 15 and 16 MB/s and is equal to or better than the 323 from 64 MB on up.
Reading, the 321's throughput is again relatively steady, but closer to the 323's.
Figure 16: Product comparison - 1000 Mbps Read
The pattern is repeated for RAID 1, with the 321 producing steady write performance and outperforming the 323 from 64 MB on up (Figure 17).
Figure 17: Product comparison - RAID 1 1000 Mbps Write
Read performance is slightly, but consistently better than the 323 for all file sizes except 32 MB (Figure 18).
Figure 18: Product comparison - RAID 1 1000 Mbps Read
In all, the 321 is better or equal to the 323 in performance, particularly for large file sizes. Depending on your filesize mix, you probably wouldn't be able to tell the difference between the two. Run your own comparisons using the NAS Charts.
I understand the push to drive product prices down and D-Link is pretty good at it. But there is so little difference between the 323 and 321, that I'm not sure that it will be worth it to D-Link to keep the two SKUs going in the long term.
Maybe this is D-Link's plan, since it isn't going out of its way to differentiate the two products from a marketing point of view (both are called 2-Bay Network Storage Enclosure, for instance). I don't have the 323's box in front of me. But I would guess that if both products were sitting side by side on a shelf, that the average buyer would be hard-pressed to tell the difference between the two, except for price.
Given that print servers thrown into routers and NASes are a crapshoot in terms of whether they'll support your printer (and chances are they won't if it's a multi-function printer), I think the choice is a no-brainer. Unless you really, really, need BitTorrent downloads in your NAS, the 321 is the way to go.