Dell OptiPlex 3040 SFF vs. Dell OptiPlex 3070 MT
Comparison and Differences
Differences between Dell OptiPlex 3040 SFF and Dell OptiPlex 3070 MT
If you are looking for the smaller form factor the Dell OptiPlex 3040 SFF is the right one for you. It is smaller than the Dell OptiPlex 3070 MT 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 Dell OptiPlex 3070 MT as it is running a newer generation CPU. This is not to say that Dell OptiPlex 3040 SFF is bad - it can still run some powerful CPUs, albeit being an older generation.
Both models have have equal amount of ram slots (2 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 3070 MT is using the faster 2666 MT/s RAM. The Dell OptiPlex 3040 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 Dell OptiPlex 3070 MT as it has the ability to run 32 GB of RAM. The Dell OptiPlex 3040 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.
The DisplayPort is usually the more popular video port used with desktops and laptops, while the HDMI is used predominantly in consumer electronics. That's why, it is good to see that both of the models come with a DisplayPort.
In case your monitor supports HDMI only, you will be happy to hear that both models come with an HDMI port.
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 3070 MT is better equipped as it comes with 3 SATA slot(s), while the Dell OptiPlex 3040 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 3070 MT. Sadly, the Dell OptiPlex 3040 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!
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 3040 SFF comes with a decent 180 Watt PSU, but the Dell OptiPlex 3070 MT has a more powerful one rated at 260 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.