Dell OptiPlex 980 SFF vs. Dell Vostro 260s
Comparison and Differences
Differences between Dell OptiPlex 980 SFF and Dell Vostro 260s
Both models have the same form factor, meaning reoughtly they have the same phiysical size and form.
Usually the newer the generation of the CPU, the better the performance and efficiency is. If your budget allows it, you should go with the Dell Vostro 260s as it is running a newer generation CPU. This is not to say that Dell OptiPlex 980 SFF is bad - it can still run some powerful CPUs, albeit being an older generation.
The Dell OptiPlex 980 SFF has 4 RAM slots while the Dell Vostro 260s has only 2 slot(s). This is not something to worry about. Just make sure you take it into consideration when planning how much RAM you are going to use.
None of the desktops has an advantage when it comes to the speed of the RAM being used. Both models support RAM speeds of up to 1333. Additionally, if you will be needing a lot of RAM, better go for the Dell OptiPlex 980 SFF as it has the ability to run 16 GB of RAM. The Dell Vostro 260s can do a bit less at max 8 GB. Most of the times, this should be sufficient for the majority of users.
In total the Dell OptiPlex 980 SFF has 10 USB ports. The Dell Vostro 260s is inferior in this regard and packs 8 USB ports. In any case, if you miss USB ports, you can always purchase a USB hub. None of the desktop models has a USB 3.1 port (10Gb/s), so if you need a fast connection to your peripherals, like external Solid State Drive, you will need to look elsewhere.
Unfortunately, only the Dell OptiPlex 980 SFF has a DisplayPort. The Dell Vostro 260s does not have one? Don't worry though, nowadays video adapters are cheap and you can get almost any combination of conversion types.
The Dell Vostro 260s comes with an HDMI port, while the Dell OptiPlex 980 SFF does not support the interface. Of course missing HDMI port is something that can be easily fixed with a good adapter (e.g. DisplayPort to HDMI).
SATA ports are placed on the system board and it is where you connect your HDD, SSD and Optical Disk Drives. More SATA slots will allow you to have more drives running at the same time. In this regard the Dell Vostro 260s is better equipped as it comes with 4 SATA slot(s), while the Dell OptiPlex 980 SFF has 3 slot(s).
M.2 SSD interface allows you to transfer data with higher speeds compared to the old SATA interface. Unfortunately, neither the Dell OptiPlex 980 SFF, nor the Dell Vostro 260s has one. However, you can still use a SATA SSD drive which should give you satisfactory performance.
Make sure that the available M.2 slot supports the PCIe (also called NVMe) interface. This is important as there are M.2 slots which support only the inferior SATA III interface. For comparison, the SATA III interface has max speeds of 6Gb/s, while the PCIe 3.0 x4 will support speeds up to 32Gb/s!
Having a Power Supply Unit with high power rating is important, if you are going to use components which require extra power. The Dell OptiPlex 980 SFF comes with a decent 235 Watt PSU, but the Dell Vostro 260s has a more powerful one rated at 250 Watts. Choosing either one depends on your specific requirements and use case. Also don't forget that some models might have more than one PSU option - try to always get the most powerful one, especially if you plan to upgrade to a powerful GPU.