Dell OptiPlex 5090 MT vs. HP ProDesk 490 G1 Microtower
Comparison and Differences
Differences between Dell OptiPlex 5090 MT and HP ProDesk 490 G1 Microtower
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 OptiPlex 5090 MT as it is running a newer generation CPU. This is not to say that HP ProDesk 490 G1 Microtower is bad - it can still run some powerful CPUs, albeit being an older generation.
Both models have have equal amount of ram slots (4 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 OptiPlex 5090 MT is using the faster 3200 MT/s RAM. The HP ProDesk 490 G1 Microtower 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 MT as it has the ability to run 128 GB of RAM. The HP ProDesk 490 G1 Microtower can do a bit less at max 32 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 10. If this is not enough, using a USB hub is always a viable option. What is nice about the Dell OptiPlex 5090 MT, is that it has 3 USB 3.1 port(s) which allows transfer of up to 10Gb/s. Unfortunately, the HP ProDesk 490 G1 Microtower 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 MT has a DisplayPort. The HP ProDesk 490 G1 Microtower 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 OptiPlex 5090 MT comes with an HDMI port, while the HP ProDesk 490 G1 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 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 MT. Sadly, the HP ProDesk 490 G1 Microtower 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 HP ProDesk 490 G1 Microtower comes with a decent 300 Watt PSU, but the Dell OptiPlex 5090 MT has a more powerful one rated at 360 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.