Apple Silicon processors feature a System-on-Chip design. The main chip contains the CPU, GPU, Neural Engine, hardware video processing engines, and more. The choice of chip makes a huge difference in the system design, regardless of which chassis (e.g., iMac, Mac mini, MacBook Air) Apple places the chip in.
Some Mac minis have M2 chips. Others have M2 Pro chips. Even though the M2 Pro is one generation behind the M3, it is a higher-end chip within its line. So, in some respects, it is a better chip than the M3.
The 24" M3 iMac and the M2 Mac mini offer
- Two USB-C (Thunderbolt) expansion ports
- A choice of 8, 16, or 24 GB of RAM (not expandable after purchase)
- Support for up to two displays, total, where the built-in display on the iMac counts against that total
The 24" M3 iMac has a very nice 4.5K Retina display, but it's only for use by the built-in computer. You can't use it as a hardware monitor for, say, a Windows or Mac laptop. The M2 Mac mini comes with two USB-A (USB 3) ports, and a HDMI port, and an Ethernet port. Some versions of the 24" M3 iMac offer two USB-C (USB 3) ports, and an Ethernet port. The cheapest versions do not – and will soon have you running out to buy a hub or dock.
The M2 Pro Mac mini offers
- Four USB-C (Thunderbolt) expansion ports
- A choice of 16 or 32 GB of RAM (not expandable after purchase)
- Support for up to three displays, total
- More CPU cores (which probably won't offer much benefit unless you run batch jobs that can make use of them)
- More GPU cores
If you load up a M2 Pro Mac mini with 32 GB of RAM and other goodies, the price may get to a point where it would make more sense to get a low-end M2 Max Mac Studio. The M2 Max Mac Studios start out with 32 GB of RAM and have several welcome front-panel additions: two USB-C (USB) ports and a SDXC card slot.