Dell OptiPlex 7050 MT vs. HP ProDesk 490 G2 Microtower
Comparison and Differences
Differences between Dell OptiPlex 7050 MT and HP ProDesk 490 G2 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 7050 MT as it is running a newer generation CPU. This is not to say that HP ProDesk 490 G2 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 7050 MT is using the faster 2400 MT/s RAM. The HP ProDesk 490 G2 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 7050 MT as it has the ability to run 64 GB of RAM. The HP ProDesk 490 G2 Microtower can do a bit less at max 32 GB. Most of the times, this should be sufficient for the majority of users.
In total the Dell OptiPlex 7050 MT has 10 USB ports. The HP ProDesk 490 G2 Microtower 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. 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 7050 MT has a DisplayPort. The HP ProDesk 490 G2 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 7050 MT comes with an HDMI port, while the HP ProDesk 490 G2 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 OptiPlex 7050 MT is better equipped as it comes with 4 SATA slot(s), while the HP ProDesk 490 G2 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 Dell OptiPlex 7050 MT. Sadly, the HP ProDesk 490 G2 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 Dell OptiPlex 7050 MT comes with a decent 240 Watt PSU, but the HP ProDesk 490 G2 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.