Dell Inspiron 620s vs. Dell OptiPlex 790 DT
Comparison and Differences
Differences between Dell Inspiron 620s and Dell OptiPlex 790 DT
If you are looking for the smaller form factor the Dell Inspiron 620s is the right one for you. It is smaller than the Dell OptiPlex 790 DT and will fit more easily under your desk.
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 Inspiron 620s as it is running a newer generation CPU. This is not to say that Dell OptiPlex 790 DT is bad - it can still run some powerful CPUs, albeit being an older generation.
Both models have have equal amount of ram slots (2 RAM). Usually two RAM slots are more than enough for most cases. However, the count should be taken into account when planning how much and what combination of RAM you are going to need for your system.
The Dell Inspiron 620s is using the faster 1600 MT/s RAM. The Dell OptiPlex 790 DT is slower by supporting RAM speeds of up to 1333 MT/s. Additionally, if you will be needing a lot of RAM, better go for the Dell OptiPlex 790 DT as it has the ability to run 16 GB of RAM. The Dell Inspiron 620s can do a bit less at max 8 GB. Most of the times, this should be sufficient for the majority of users.
Both models have the same amount of USB ports for total count of 8. If this is not enough, using a USB hub is always a viable option. 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 790 DT has a DisplayPort. The Dell Inspiron 620s 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 Inspiron 620s comes with an HDMI port, while the Dell OptiPlex 790 DT 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 Inspiron 620s is better equipped as it comes with 4 SATA slot(s), while the Dell OptiPlex 790 DT 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 790 DT, nor the Dell Inspiron 620s 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!
Looking at the Power Supply Unit (PSU) of the two models we don't see any differences. For either of them you get a maximum power of 250 Watts. However be careful, many models have more than one power supply option. When buying your computer, it is a good idea to get a version with the most powerful PSU. This will potentially allow you to upgrade to a more powerful GPU for example.