Dell Vostro 3902 vs. HP ProDesk 400 G5 Microtower
Comparison and Differences
Differences between Dell Vostro 3902 and HP ProDesk 400 G5 Microtower
If you are looking for a more modern desktop, then you should go with the HP ProDesk 400 G5 Microtower which was released in 2018. The Dell Vostro 3902 is older and entered production in 2014.
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 HP ProDesk 400 G5 Microtower 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.
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 HP ProDesk 400 G5 Microtower is using the faster 2666 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 HP ProDesk 400 G5 Microtower as it has the ability to run 32 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.
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 HP ProDesk 400 G5 Microtower 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 HP ProDesk 400 G5 Microtower 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 3902 is better equipped as it comes with 4 SATA slot(s), while the HP ProDesk 400 G5 Microtower has 3 slot(s).
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 HP ProDesk 400 G5 Microtower. 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!
Having a Power Supply Unit with high power rating is important, if you are going to use components which require extra power. The Dell Vostro 3902 comes with a decent 300 Watt PSU, but the HP ProDesk 400 G5 Microtower has a more powerful one rated at 310 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.