HP ProDesk 400 G1 SFF vs. HP ProDesk 490 G3 Microtower
Comparison and Differences
Differences between HP ProDesk 400 G1 SFF and HP ProDesk 490 G3 Microtower
If you are looking for the smaller form factor the HP ProDesk 400 G1 SFF is the right one for you. It is smaller than the HP ProDesk 490 G3 Microtower 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 HP ProDesk 490 G3 Microtower as it is running a newer generation CPU. This is not to say that HP ProDesk 400 G1 SFF is bad - it can still run some powerful CPUs, albeit being an older generation.
The HP ProDesk 490 G3 Microtower has 4 RAM slots while the HP ProDesk 400 G1 SFF 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 HP ProDesk 490 G3 Microtower is using the faster 2133 MT/s RAM. The HP ProDesk 400 G1 SFF 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 490 G3 Microtower as it has the ability to run 64 GB of RAM. The HP ProDesk 400 G1 SFF 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 490 G3 Microtower has a DisplayPort. The HP ProDesk 400 G1 SFF does not have one? Don't worry though, nowadays video adapters are cheap and you can get almost any combination of conversion types.
None of the models has an HDMI port. If your monitor supports only the HDMI interface, you will need to buy an adapter. Such adapters are cheap so nothing to worry about.
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 3 SATA slot(s). Keep in mind that having too few SATA slots might limit your options for connecting additional memory drives.
M.2 SSD interface allows you to transfer data with higher speeds compared to the old SATA interface. Unfortunately, neither the HP ProDesk 400 G1 SFF, nor the HP ProDesk 490 G3 Microtower 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 HP ProDesk 400 G1 SFF comes with a decent 240 Watt PSU, but the HP ProDesk 490 G3 Microtower has a more powerful one rated at 300 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.