Alienware X51 R3 vs. HP ProDesk 600 G4 Microtower
Comparison and Differences
Differences between Alienware X51 R3 and HP ProDesk 600 G4 Microtower
If you are looking for a more modern desktop, then you should go with the HP ProDesk 600 G4 Microtower which was released in 2018. The Alienware X51 R3 is older and entered production in 2015.
If you are looking for the smaller form factor the Alienware X51 R3 is the right one for you. It is smaller than the HP ProDesk 600 G4 Microtower and will fit more easily under your desk.
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 600 G4 Microtower as it is running a newer generation CPU. This is not to say that Alienware X51 R3 is bad - it can still run some powerful CPUs, albeit being an older generation.
Memory
The HP ProDesk 600 G4 Microtower has 4 RAM slots while the Alienware X51 R3 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 600 G4 Microtower is using the faster 2666 MT/s RAM. The Alienware X51 R3 is slower by supporting RAM speeds of up to 2133 MT/s. Additionally, if you will be needing a lot of RAM, better go for the HP ProDesk 600 G4 Microtower as it has the ability to run 64 GB of RAM. The Alienware X51 R3 can do a bit less at max 32 GB. Most of the times, this should be sufficient for the majority of users.
Ports
In total the HP ProDesk 600 G4 Microtower has 11 USB ports. The Alienware X51 R3 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. It's great that both of the models have USB 3.1 ports which will allow you to exchange data with your peripherals at up to 10Gb/s. But if you need maximum connectivity, go with the HP ProDesk 600 G4 Microtower as it has 5 USB3.1 ports (the Alienware X51 R3 has 2).
DisplayPort is crucial for any desktop machine. It is good to see that both models are featuring DisplayPorts. However, the HP ProDesk 600 G4 Microtower comes with 2 ports, while the Alienware X51 R3 has only 1. If you are planning to use multiple monitors, the HP ProDesk 600 G4 Microtower is the better choice.
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 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 HP ProDesk 600 G4 Microtower is better equipped as it comes with 4 SATA slot(s), while the Alienware X51 R3 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 600 G4 Microtower. Sadly, the Alienware X51 R3 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
Having a Power Supply Unit with high power rating is important, if you are going to use components which require extra power. The Alienware X51 R3 comes with a decent 330 Watt PSU, but the HP ProDesk 600 G4 Microtower has a more powerful one rated at 400 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.