Dell OptiPlex 5090 SFF vs. Dell Vostro 3902
Comparison and Differences
Differences between Dell OptiPlex 5090 SFF and Dell Vostro 3902
If you are looking for the smaller form factor the Dell OptiPlex 5090 SFF is the right one for you. It is smaller than the Dell Vostro 3902 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 OptiPlex 5090 SFF as it is running a newer generation CPU. This is not to say that Dell Vostro 3902 is bad - it can still run some powerful CPUs, albeit being an older generation.
The Dell OptiPlex 5090 SFF has 4 RAM slots while the Dell Vostro 3902 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.
The Dell OptiPlex 5090 SFF is using the faster 3200 MT/s RAM. The Dell Vostro 3902 is slower by supporting RAM speeds of up to 1600 MT/s. Additionally, if you will be needing a lot of RAM, better go for the Dell OptiPlex 5090 SFF as it has the ability to run 128 GB of RAM. The Dell Vostro 3902 can do a bit less at max 16 GB. Most of the times, this should be sufficient for the majority of users.
In total the Dell OptiPlex 5090 SFF has 10 USB ports. The Dell Vostro 3902 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. What is nice about the Dell OptiPlex 5090 SFF, is that it has 1 USB 3.1 port(s) which allows transfer of up to 10Gb/s. Unfortunately, the Dell Vostro 3902 has no such port, thus restricting your transfer speeds significantly. For people who want to use external drives on regular basis, this might be an issue.
Unfortunately, only the Dell OptiPlex 5090 SFF has a DisplayPort. The Dell Vostro 3902 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 3902 comes with an HDMI port, while the Dell OptiPlex 5090 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 slots are located on the motherboard and it is where SSD, HDD and Optical Disk Drives are connected. Each of the two models being compared have 4 SATA slot(s). Keep in mind that having too few SATA slots might limit your options for connecting additional memory drives.
If you want the fastest transfer speeds for your SSD, an M.2 interface is crucial. Thus, if the M.2 SSD slot is a mandatory requirement for you, go with the Dell OptiPlex 5090 SFF. Sadly, the Dell Vostro 3902 has no such slot, and you will be forced to use the SATA interface instead.
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 300 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.