Dell OptiPlex 7040 SFF vs. HP ProDesk 400 G4 SFF
Comparison and Differences
Differences between Dell OptiPlex 7040 SFF and HP ProDesk 400 G4 SFF
If you are looking for a more modern desktop, then you should go with the HP ProDesk 400 G4 SFF which was released in 2017. The Dell OptiPlex 7040 SFF is older and entered production in 2015.
Both models have the same form factor, meaning reoughtly they have the same phiysical size and form.
Processor
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 G4 SFF as it is running a newer generation CPU. This is not to say that Dell OptiPlex 7040 SFF is bad - it can still run some powerful CPUs, albeit being an older generation.
Memory
The Dell OptiPlex 7040 SFF has 4 RAM slots while the HP ProDesk 400 G4 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 400 G4 SFF is using the faster 2400 MT/s RAM. The Dell OptiPlex 7040 SFF is slower by supporting RAM speeds of up to 2133 MT/s. In addition, you will be able to install the same amount of RAM in both models, and most probably 64 GB of RAM will be enough for most people. However, if you will be needing more RAM, make sure to check other desktop models too.
Ports
In total the Dell OptiPlex 7040 SFF has 10 USB ports. The HP ProDesk 400 G4 SFF 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.
DisplayPort is crucial for any desktop machine. It is good to see that both models are featuring DisplayPorts. However, the Dell OptiPlex 7040 SFF comes with 2 ports, while the HP ProDesk 400 G4 SFF has only 1. If you are planning to use multiple monitors, the Dell OptiPlex 7040 SFF is the better choice.
The Dell OptiPlex 7040 SFF comes with an HDMI port, while the HP ProDesk 400 G4 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 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 7040 SFF is better equipped as it comes with 3 SATA slot(s), while the HP ProDesk 400 G4 SFF has 2 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 7040 SFF. Sadly, the HP ProDesk 400 G4 SFF 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!
Power Supply
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 180 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.
Motherboard
